Document:

<PAGE>   1

                                                                    EXHIBIT 10.7

                                      LEASE

                  THE PRUDENTIAL INSURANCE COMPANY OF AMERICA,
                            a New Jersey corporation
                                  (as Landlord)

                                       and

                               EXACTIS.COM. INC.,
                             a Delaware corporation
                                   (as Tenant)

<PAGE>   2

                                      LEASE

                  THE PRUDENTIAL INSURANCE COMPANY OF AMERICA,
                            a New Jersey corporation
                                  (as Landlord)

                                       and

                    EXACTIS.COM, INC., a Delaware corporation
                                   (as Tenant)

<TABLE>
<CAPTION>
   Paragraph                                                               Page
   ---------                                                               ----
<S>                                                                        <C>
1.   PREMISES ...............................................................  1

2.   TERM ...................................................................  1

3.   RENT ...................................................................  1

4.   COMPLETION OR REMODELING OF THE PREMISES ...............................  1

5.   OPERATING EXPENSES .....................................................  2

6.   SERVICES ...............................................................  8

7.   QUIET ENJOYMENT ........................................................ 10

8.   DEPOSIT ................................................................ 10

9.   CHARACTER OF OCCUPANCY ................................................. 10

10.  MAINTENANCE, ALTERATIONS AND REENTRY BY LANDLORD ....................... 11

11.  ALTERATIONS AND REPAIRS BY TENANT ...................................... 11

12.  MECHANICS' LIENS ....................................................... 13

13.  SUBLETTING AND ASSIGNMENT .............................................. 13

14.  DAMAGE TO PROPERTY ..................................................... 15

15.  INDEMNITY TO LANDLORD .................................................. 15

16.  SURRENDER AND NOTICE ................................................... 16

17.  INSURANCE, CASUALTY, AND RESTORATION OF PREMISES ....................... 16

18.  CONDEMNATION ........................................................... 17

19.  DEFAULT BY TENANT ...................................................... 17

20.  DEFAULT BY LANDLORD .................................................... 20

21.  SUBORDINATION AND ATTORNMENT ........................................... 21

22.  REMOVAL OF TENANT'S PROPERTY ........................................... 21

23.  HOLDING OVER: TENANCY MONTH-TO-MONTH ................................... 21

24.  PAYMENTS AFTER TERMINATION ............................................. 22

25.  STATEMENT OF PERFORMANCE ............................................... 22

26.  MISCELLANEOUS .......................................................... 22

27.  AUTHORITIES FOR ACTION AND NOTICE ...................................... 24

28.  RULES AND REGULATIONS .................................................. 24

29.  PARKING ................................................................ 24

30.  SUBSTITUTE PREMISES .................................................... 25
</TABLE>

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<TABLE>
<S>                                                                        <C>
31.  BROKERAGE .............................................................. 25

32.  ERISA .................................................................. 25

33.  TIME OF ESSENCE ........................................................ 26
</TABLE>

<TABLE>
<CAPTION>
                            EXHIBITS/ATTACHMENTS LIST
                            -------------------------
<S>                             <C>
                    Exhibit A   Floor Plan
                    Exhibit B   Legal Description
                    Exhibit C   Commencement Certificate
                    Exhibit D   Rules and Regulations
                    Exhibit E   Letter of Credit
                    Exhibit F   Work Letter
                    Exhibit G   Tank License
                    Exhibit H   Expansion Space
</TABLE>

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<PAGE>   4

                              OFFICE BUILDING LEASE

         THIS LEASE is made this 19th day of January, 2000, by and between
THE PRUDENTIAL INSURANCE COMPANY OF AMERICA, a New Jersey corporation
("Landlord") and EXACTIS.COM, INC., a Delaware corporation ("Tenant").

                             W I T N E S S E T H :

         1. PREMISES. In consideration of the payment of rent and the keeping
and performance of the covenants and agreements by Tenant, as hereinafter set
forth, Landlord hereby leases and demises unto Tenant the premises located on
the 4th and 5th floors of the Building, known as Suite 500 comprised of
approximately 46,418 rentable square feet (hereinafter referred to as the
"Premises"), as depicted on the plat hereto attached as Exhibit A, and being a
part of the building known as Johns Manville Plaza, located at 717 17th Street,
Denver, Colorado (the "Building"), together with a non-exclusive right, subject
to the provisions hereof, to use all appurtenances thereto, including, but not
limited to, any plazas, common areas, or other areas on the real property
(described more particularly on Exhibit B "Real Property") designated by
Landlord for the exclusive or non-exclusive use of the tenants of the Building.
The Building, Real Property, plazas, common areas, other areas, and
appurtenances are hereinafter collectively sometimes called the "Building
Complex."

         2. TERM. The term of the Lease shall commence at 12:01 a.m. on the 1st
day of March, 2000 (subject to the terms of the Work Letter), and shall
terminate at 12:00 midnight on the 28th day of February, 2010, (said ten-year
term is referred to herein as the "Primary Lease Term").

         3. RENT. Tenant shall pay the annual rental for the Primary Lease Term
in the monthly amounts of:

<TABLE>
<CAPTION>
            Period                         Monthly Base Rent
            ------                         -----------------
<S>                                        <C>
March 1, 2000-February 28, 2001            $77,363.33
March 1, 2001-February 28, 2002            $81,231.50
March 1, 2002-February 29, 2004            $88,967.83
March 1, 2004-February 28, 2006            $96,704.17
March 1, 2006-February 29, 2008            $104,440.50
March 1, 2008-February 28, 2010            $112,176.83
</TABLE>

(the "Base Rent"), commencing March 1, 2000, and continuing on the first day of
each month thereafter during the term hereof. All rents shall be paid in
advance, without notice, set off, abatement, or diminution, at the office of
Landlord in Denver, Colorado, or at such place as Landlord from time to time
designates in writing. Tenant shall prepay the first three month's Base Rent
upon the execution hereof, which shall be credited against such amount as of the
date that Tenant's rental obligations commence. Notwithstanding anything to the
contrary stated herein, Tenant shall have the right to occupy for purposes of
installing and operating a computer facility in a portion of the Premises
designated as Tenant's computer room, consisting of approximately ________
rentable square feet on the 5th floor (the "Computer Room"), commencing on the
date that is seven (7) days following completion of the Tenant Finish Work in
the Computer Room. Tenant's occupancy of the Computer Room prior to the
commencement of the Primary Lease Term shall be subject to all terms of the
Lease, including payment of the monthly Base Rent calculated on the basis of an
annual rate of $20.00 per rentable square foot. Except for the foregoing, Tenant
shall not be obligated for payment of Rent during the time Tenant occupies the
Premises prior to the Commencement Date for construction of the Tenant Finish
Work (as defined in the Work Letter).

     4. COMPLETION OR REMODELING OF THE PREMISES.

            A. Provisions regarding any remodeling of or tenant finish work to
be completed in the Premises, if any, shall be set forth in a work letter
attached to this Lease as an exhibit (the "Work Letter"). Except as set forth in
the Work Letter or elsewhere in this Lease, Landlord shall have no obligations
for the completion or remodeling of the Premises, and Tenant shall accept the
Premises in their "as is" condition on the date the Primary Lease Term
commences. If Landlord is delayed in delivering the Premises to Tenant

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then the obligation for the payment of rent and the commencement of the Primary
Lease Term hereof shall be postponed until Landlord delivers the Premises to
Tenant whereupon all of the covenants, conditions, and agreements cOntained
herein shall be in full force and effect. The postponement of Tenant's
obligation to pay rent and other sums hereunder shall be in full settlement of
all claims which Tenant may otherwise have by reason of such delay of delivery.

            B. If the commencement of the Primary Lease Term is delayed pursuant
to subparagraph A above or any provision of the Work Letter, and such
commencement date would otherwise occur on other than the first day of the
month, the commencement date of the Primary Lease Term shall be further delayed
until the first day of the following month and Tenant shall pay proportionate
rent at the same monthly rate set forth herein (also in advance) for such
partial month. In the event said commencement date is so delayed, the expiration
of the term hereof shall be extended so that the Primary Lease Term will
continue for the full period set forth in Paragraph 2 hereof. As soon as the
Primary Lease Term commences, Landlord and Tenant shall execute a commencement
certificate in the form attached hereto as Exhibit C, which may be requested by
either party, setting forth the exact date on which the Primary Lease Term
commenced and the expiration date of the Primary Lease Term.

            C. Except. as provided in the Work Letter attached hereto, taking
possession of the Premises by Tenant shall be conclusive evidence as against
Tenant that the Premises were in the condition agreed upon between Landlord and
Tenant and acknowledgment of satisfactory completion of any fix-up or
remodeling, as the case may be, which Landlord has agreed in writing to perform.

         5. OPERATING EXPENSES.

            A. Definitions. In addition to terms hereinabove defined, the
following terms shall have the following meanings with respect to the provisions
of this Lease:

               (1) "Base Operating Expenses" shall mean an amount equal to the
Operating Expenses (as hereinafter defined) for the calendar year 2000, as
determined by Landlord following the end of such year, in accordance with this
Paragraph 5. It is understood and acknowledged by Tenant that Landlord has not
made any representation or given Tenant any assurances that the Base Operating
Expenses will equal any specified amounts (any estimate provided by Landlord
being deemed non-binding estimates only).

               (2) "Landlord's Accountants" shall mean that individual or firm
employed by Landlord from time to time to keep the books and records for the
Building Complex, and/or to prepare the federal and state income tax returns for
Landlord with respect to the Building Complex, all of which books and records
shall be certified to by an appropriate representative of Landlord.

               (3) "Building Standard" means the level of tenant finish
improvements or the level of Building services, as the context may require,
customarily offered from time to time by Landlord to all tenants of the
Building.

               (4) "Rentable Area" shall mean 672,343 rentable square feet. If
there is a significant change in the aggregate Rentable Area as a result of an
addition to the Building, partial destruction thereof, modification to building
design, or similar cause which causes a reduction or increase thereto on a
permanent basis, Landlord's Accountants shall make such adjustments in the
computations as shall be necessary to provide for any such change.

               (5) "Tenant's Pro Rata Share" shall mean, subject to the
limitations hereinafter set forth, a fraction, the numerator of which is the
rentable square feet comprising the Premises and the denominator of which is
the Rentable Area. In the event Tenant, at any time during the Primary Lease
Term, or any extensions thereof, leases additional space in the Building,
Tenant's Pro Rata Share shall be recomputed by dividing the total rentable
square footage of space then being leased by Tenant (including any additional
space) by the Rentable Area and the resulting figure shall become Tenant's Pro
Rata Share.

               (6) "Operating Expense Year" shall mean each calendar year during
the term of this Lease, except that the first Operating Expense Year shall begin
on the date the Primary Lease Term commences and end on December 31 of such year
and the last Operating Expense Year shall begin on January 1 of the year in

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<PAGE>   6

which this Lease expires or is terminated and end on the date of such expiration
or termination. In the case of an Operating Expense Year of less than twelve
(12) months, Operating Expenses for such year shall be prorated.

               (7) "Operating Expenses" shall mean all operating expenses of any
kind or nature which are necessary, ordinary, or customarily incurred in
connection with the operation and maintenance of the Building Complex as
determined by Landlord's Accountants. Operating Expenses shall include, but not
be limited to:

               (a) All real property taxes and assessments levied against the
     Building Complex by any governmental or quasi-governmental authority. The
     foregoing shall include any taxes, assessments, surcharges, or service or
     other fees of a nature not presently in effect which shall hereafter be
     levied on the Building Complex as a result of the use, ownership or
     operation of the Building Complex or for any other reason, whether in lieu
     of or in addition to, any current real estate taxes and assessments;
     provided, however, any taxes which shall be levied on the rentals of the
     Building Complex shall be determined as if the Building Complex were
     Landlord's only property and, provided, further, that in no event shall
     the term "taxes or assessments," as used herein, include any net federal or
     state income taxes levied or assessed on Landlord, unless such taxes are a
     specific substitute for real property taxes. Such term shall, however,
     include gross taxes on rentals. Expenses incurred by Landlord for tax
     consultants and in contesting the amount or validity of any such taxes or
     assessments shall be included in such computations (all of the foregoing
     are collectively referred to herein as the "Taxes"). "Assessment" shall
     include so-called special assessments, license tax, business license fee,
     business license tax, commercial rental tax, levy, charge penalty or tax,
     imposed by any authority having the direct power to tax, including any
     city, county, state or federal government, or any school, agricultural,
     lighting, water, drainage or other improvement or special district
     thereof, against the Premises, the Building or Building Complex or any
     legal or equitable interest of Landlord therein. For the purposes of this
     Lease, any special assessments shall be deemed payable in such number of
     installments as is permitted by law, whether or not actually so paid and
     shall include any applicable interest on such installments (if such
     interest is actually paid by Landlord);

               (b) Costs of supplies for maintenance of the Building, including,
     but not limited to, the cost of relamping and replacing ballasts in all
     Building Standard tenant lighting as the same may be required from time to
     time;

               (c) Costs incurred in connection with obtaining and providing
     energy for the Building Complex, including, but not limited to, costs of
     propane, butane, natural gas, steam, electricity, solar energy and fuel
     oils, coal or any other energy sources;

               (d) Costs of water and sanitary and storm drainage services;

               (e) Costs of janitorial and security services and systems;

               (f) Costs of general maintenance and repairs, including costs
     under HVAC and other mechanical maintenance contracts, carpet replacement
     and painting in Common Areas; and repairs and replacements of equipment
     used in connection with such maintenance and repair work;

               (g) Costs of maintenance and replacement of landscaping;

               (h) Insurance premiums, including fire and all-risk or
     multi-peril coverage, together with loss of rent endorsement, if
     applicable; the part of any claim required to be paid under the deductible
     portion of any insurance policy carried by Landlord in

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<PAGE>   7

     connection with the Building Complex (where Landlord is unable to obtain
     insurance without such deductible from a major insurance carrier at
     reasonable rates); public liability insurance; and any other insurance
     carried by Landlord on the Building Complex or any component parts
     thereof (all such insurance shall be in such amounts as may be required
     by any Mortgagee [as defined in Paragraph 20 hereof] or as Landlord may
     reasonably determine);

               (i) Labor costs, including wages and other payments, costs to
     Landlord of workmen's compensation and disability insurance, payroll taxes,
     welfare fringe benefits, and all legal fees and other costs or expenses
     incurred in resolving any labor dispute;

               (j) Professional building management fees of no more than 2.5% of
     gross collections of Rent, costs and expenses, including costs of office
     space and storage space and leasing or amortized costs of acquisition of
     office furniture and equipment required by management for performance of
     its services as contemplated herein;

               (k) Legal, accounting, inspection, and other consultation fees
     (including, without limitation, fees charged by consultants retained by
     Landlord for services that are designed to produce a reduction in Operating
     Expenses or to reasonably improve the operation, maintenance or state of
     repair of the Building Complex) incurred in the ordinary course of
     operating the Building Complex;

               (l) The costs of capital improvements and structural repairs and
     replacements made in or to the Building Complex in order to conform to
     changes subsequent to the effective date of this Lease in any applicable
     laws, ordinances, rules, regulations, or orders of any governmental or
     quasi-governmental authority having jurisdiction over the Building Complex
     or parts and supplies therein (herein "Required Capital Improvements"); and
     the costs of any capital improvements and structural repairs and
     replacements that reduce Operating Expenses (herein "Cost Savings
     Improvements"). The expenditures for Required Capital Improvements and Cost
     Savings Improvements shall be amortized at a market rate of return over the
     useful life of such capital improvement or structural repair or replacement
     (as determined by Landlord's Accountants); provided that the amortized
     amount of any Cost Savings Improvement in any year will be equal to the
     estimated reduction in Operating Expenses as a result thereof; and

               (m) Costs incurred by Landlord's Accountants in engaging experts
     or other consultants to assist them in making the computations required
     hereunder.

"Operating Expenses" shall not include:

               (1) Costs of work, including painting and decorating and tenant
     change work, which Landlord performs for any tenant or in any tenant's
     space in the Building;

               (2) Costs of repairs or other work occasioned by fire, windstorm
     or other insured casualty to the extent of insurance proceeds received;

               (3) Leasing commissions, advertising expenses, and other costs
     incurred in leasing space in the Building;

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<PAGE>   8

                (4) Costs of repairs or rebuilding necessitated by condemnation;

                (5) Interest, principal, points and fees on debt or amortization
     on any mortgage or mortgagees or any other debt instrument encumbering the
     Building;

                (6) Depreciation on the Building;

                (7) Any ground lease rental affecting all or a portion of the
     Building;

                (8) Costs incurred by Landlord for the repair of damage to the
     Building or as a result of Landlord's gross negligence or willful
     misconduct, to the extent that Landlord is reimbursed by a third party or
     insurance proceeds;

                (9) Costs incurred by Landlord for alterations which are
     considered capital improvements and replacements under generally accepted
     accounting principles, consistently applied, except as provided in
     (5(A)(7)(1) above;

               (10) Expenses in connection with services or other benefits which
     are not offered to Tenant, or for which Tenant is charged directly but
     which are not provided to another tenant or occupant of the Building;

               (11) Costs incurred by Landlord due to the violation by Landlord
     or any other tenant of the Building of the terms and conditions of any
     lease of space in the Building;

               (12) Overhead and profit increments paid to Landlord or to
     subsidiaries or affiliates of Landlord for services in the Building to the
     extent the same exceeds the cost of such services rendered at the same
     level of service for similar quality buildings in Denver, by unaffiliated
     third parties on a competitive basis;

               (13) Landlord's general corporate overhead and general
     administrative expenses;

               (14) Any compensation paid to clerks, attendants or other persons
     in commercial concessions operated by Landlord or in parking garages for
     the Building;

               (15) All items and services for which Tenant or any other tenant
     of the Building reimburses Landlord (other than through the pass-through of
     Operating Expenses) and which Landlord provides selectively to one or more
     tenants (other than Tenant) without reimbursement;

               (16) Advertising and promotional expenditures, and costs of
     purchase and installation of signs in or on the Building (except for the
     Building directory) identifying the owner of the Building;

               (17) Electrical power costs for which any tenant directly
     contracts with the local public service company;

               (18) Labor or other costs incurred in connection with any
     operation of any restaurant or garage in the Building;

               (19) Tax penalties incurred as a result of Landlord's negligence
     or inability or unwillingness to make payments when due or legal fees in
     connection therewith or incurred contesting such penalties;

               (20) Any other expenses which, in accordance with customary
     industry practice, would not normally be treated as Operating Expenses by
     landlords of comparable similar institutional quality office buildings;

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<PAGE>   9

               (21) Any costs, fines or penalties incurred due to violations by
     Landlord of any government rule or authority;

               (22) Purchase price of sculpture, Paintings, or other objects of
     art placed in common areas of the Building; and

               (23) Wages, salaries, medical, surgical and general welfare
     benefits, pension payments, payroll taxes, workers' compensation costs or
     other compensation paid to or for any executive employees above the grade
     of building manager.

Notwithstanding anything contained herein to the contrary, if any lease entered
into by Landlord with any tenant in the Building is on a so-called "net" basis,
or provides for a separate basis of computation for any Operating Expenses with
respect to its leased premises, then, to the extent that Landlord's Accountants
determine that an adjustment should be made in making the computations herein
provided for, Landlord's Accountants shall be permitted to modify the
computation of Base Operating Expenses, Rentable Area, and Operating Expenses
for a particular Operating Expense Year in order to eliminate or otherwise
modify any such expenses which are paid for in whole or in part by such tenant.
Furthermore, in making any computations contemplated hereby, Landlord's
Accountants shall also be permitted to make such adjustments and modifications
to the provisions of this Paragraph 5 as shall be reasonably necessary to
achieve the intention of the parties hereto.

         B. If any increase occurs in Operating Expenses during any Operating
Expense Year during the Primary Lease Term, or any extension thereof, including
the first Operating Expense Year, in excess of the Base Operating Expenses,
Tenant shall pay to Landlord Tenant's Pro Rata Share of the amount of such
increaSe. All amounts required to be paid by Tenant as a result of any such
increase shall be paid within thirty (30) days following billing therefor by
Landlord. In addition to the foregoing, it is agreed that, during each Operating
Expense Year beginning with the first month of the second Operating Expense Year
and continuing each month thereafter during the Primary Lease Term, or any
extension thereof, Tenant shall pay to Landlord, at the same time as the Base
Rent is paid, an amount equal to one-twelfth (1/12) of Landlord's estimate (as
determined by Landlord's Accountants) of Tenant's Pro Rata Share of any
projected increases in the Operating Expenses for the particular Operating
Expense Year in excess of the Base Operating Expenses, with a final adjustment
to be made between the parties at a later date for said Operating Expense Year.
In computing the increase in the monthly rental payments. based upon Tenant`s
Pro Rata Share of the estimated increase of Operating Expenses for any
particular Operating Expense Year, Landlord's Accountants shall take into
account any prior increases in the monthly rental payments attributable to
Tenant's Pro Rata Share of previously estimated increases. If, during any
Operating Expense Year, Landlord's projected increase in Operating Expenses for
said year over the Base Operating Expenses is less than the projected increase
for the previous Operating Expense Year on which Tenant's monthly rental
payments for said year were based, the rental payments to be paid by Tenant for
the new Operating Expense Year shall be decreased accordingly; provided,
however, in no event will the rental to be paid by Tenant hereunder ever be less
than the Base Rent.

      As soon as practicable following the end of each Operating Expense Year
during the Primary Lease Term, or any extension thereof, including the first
Operating Expense Year, Landlord shall submit to Tenant a statement prepared by
a representative of Landlord setting forth the exact amount of Tenant's Pro
Rata Share of the increase, if any, of the Operating Expenses for the Operating
Expense Year just completed over the Base Operating Expenses. Beginning with
said statement for the second Operating Expense Year, it shall also set forth
the difference, if any, between Tenant's actual Pro Rata Share of the increase
in Operating Expenses for such Operating Expense Year just completed and the
estimated amount of Tenant's Pro Rata Share of such increase on the basis of
which Tenant's monthly rent was computed for such particular Operating Expense
Year. Each such statement shall also set forth the projected increase, if any,
in Operating Expenses for the new Operating Expense Year over the Base
Operating Expenses and the corresponding increase or decrease in Tenant's
monthly rent for such new Operating Expense Year above or below the rental paid
by Tenant for the immediately preceding Operating Expense Year computed in
accordance with the foregoing provisions. To the extent that Tenant's Pro Rata
Share of the increase in Operating Expenses for the period covered by such
statement is different from the estimated amount upon which Tenant paid rent
during the Operating Expense Year just completed, Tenant shall pay to Landlord
the difference in cash within thirty (30) days following receipt by Tenant of
such statement from Landlord or

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receive a credit on the next months' rental owing hereunder, as the case may be.
Until Tenant receives such statement, Tenant's monthly rent for the new
Operating Expense Year shall continue to be paid at the rate paid for the
particular Operating Expense Year just completed, but Tenant shall commence
payment to Landlord of the monthly installments of rent on the basis of said
statement beginning on the first day of the month following the month in which
Tenant receives such statement. Moreover, Tenant shall pay to Landlord or deduct
from the rent, as the case may be, on the date required for the first payment of
rent, as adjusted, the difference, if any, between the monthly installments of
rent so adjusted for the new Operating Expense Year and the monthly installments
of rent actually paid during the new Operating Expense Year. In addition to the
above, if, during any particular Operating Expense Year, there is a change in
the information on which Landlord's Accountants based the estimate upon which
Tenant is then making its estimated rental payments so that such estimate
furnished to Tenant is no longer accurate, Landlord shall be permitted to revise
such estimate by notifying Tenant and there shall be such adjustments made in
the monthly rental on the first day of the month following the serving of such
statement on Tenant as shall be necessary by either increasing or decreasing, as
the case may be, the amount of monthly rent then being paid by Tenant for the
balance of the Operating Expense Year (but in no event shall any such decrease
result in a reduction of the rent below the Base Rent), as well as an
appropriate adjustment in cash based upon the amount theretofore paid by Tenant
during such particular Operating Expense Year pursuant to the prior estimate.

      Landlord's and Tenant's responsibilities with respect to the Operating
Expense adjustment described herein shall survive the expiration or early
termination of this Lease.

      In the event the Rentable Area is not fully occupied during any particular
Operating Expense Year (including the Year 2000), Landlord's Accountants may
adjust those Operating Expenses which are affected by the occupancy rates for
the particular Operating Expense Year, or portion thereof, as the case may be,
to reflect an occupancy of ninety-five percent (95%) of all such Rentable Area.

         C. If Tenant shall dispute the amount of an adjustment submitted by
Landlord's Accountants or the proposed estimated increase or decrease on the
basis of which Tenant's rent is to be adjusted as provided in subparagraph B
above, Tenant shall give Landlord written notice of such dispute within thirty
(30) days after Landlord's Accountants advise Tenant of such adjustment or
proposed increase or decrease. If Tenant does not give Landlord such notice
within such time, Tenant shall have waived its right to dispute the amounts so
determined. If Tenant timely objects, Tenant shall have the right to engage its
own certified public accountants ("Tenant's Accountants") for the purpose of
verifying the accuracy of the statement complained of or the reasonableness of
the estimated increase or decrease. If Tenant's Accountants determine that an
error has been made, Landlord's Accountants and Tenant's Accountants shall
endeavor to agree upon the matter, failing which the parties shall submit such
matter to an independent certified public accountant selected by Landlord and
reasonably acceptable to Tenant, for a determination which shall be final,
conclusive and binding upon Landlord and Tenant. All costs incurred by Tenant
in obtaining its own accountants shall be paid for by Tenant unless Tenant's
Accountants disclose an error, acknowledged by Landlord's Accountants (or found
to have occurred in a judicial action), of more than four percent (4%) in the
computation of the total amount of Operating Expenses as set forth in the
statement submitted by Landlord's Accountants which is challenged, in which
event Landlord shall pay the reasonable costs incurred by Tenant in obtaining
such audit. Notwithstanding the pendency of any dispute over any particular
statement, Tenant shall continue to pay Landlord the amount of the adjusted
monthly installments of rent determined by Landlord's Accountants until the
adjustment has been determined to be incorrect as aforesaid. If it shall be
determined that any portion of the Operating Expenses were not properly
chargeable to Tenant, then Landlord shall promptly credit or refund the
appropriate sum to Tenant. Delay by Landlord or Landlord's Accountants in
submitting any statement contemplated herein for any Operating Expense Year
shall not affect the provisions of this Paragraph 5 or constitute a waiver of
Landlord's rights as set forth herein for said Operating Expense Year or any
subsequent Operating Expense Years during the Primary Lease Term and any
extensions thereof.

         D. Notwithstanding anything to the contrary set forth herein, for the
purposes of calculating Tenant's Pro Share of Operating Expenses. "Controlled
Expenses" (as hereinafter defined) shall not exceed the "Maximum Controlled

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Expenses" (as hereinafter defined). "Controlled Expenses" shall mean all
Operating Expenses except those attributable to Taxes, costs of insurance,
including, without limitation, liability insurance, casualty insurance and
worker's compensation insurance, costs of utilities, and costs of compliance
with any laws, rules or regulations as provided in Paragraph 5.A(7)(1). If
Landlord is managing the Building itself the management fees included within
Operating Expenses shall be a Controlled Expense. "Maximum Controlled Expenses"
shall mean: (a) for calendar year 2000, the full amount of the actual expenses
for Controlled Expenses as determined in accordance with the foregoing
provisions: (b) for calendar year 2001 and each calendar year thereafter, the
prior calendar year's Maximum Controlled Expenses multiplied by 1.05. The
limitations described above shall be a limitation only on the calculation and
passthrough to Tenant of Tenant's Pro Rata Share of Operating Expenses and such
limitation shall not prohibit Landlord from spending amounts in excess of such
limitations. Landlord may, in accordance with advice from its accountants and
other professionals, reasonably contest any utility rate increases associated
with the Building and/or tax assessments and to apply for all rebates to which
it is entitled so long as it has knowledge thereof. The costs of all such
contests and applications shall be included in Operating Expenses, however, any
penalties or fines in connection with such amounts shall not be so included. To
the extent any rebates or refunds are actually received by Landlord, they shall
be applied to reduce the total Operating Expenses for the year in which such
amounts are received. If any such amounts attributable to periods during the
term hereof are received by Landlord following the expiration of the term hereof
(according to its terms and not as a result of an Event of Default, as
hereinafter defined), Landlord agrees to forward to Tenant any amounts to which
Tenant is entitled as and when received notwithstanding the fact that this
Lease has so expired, provided Tenant has given to Landlord a valid forwarding
address.

      6. SERVICES.

         A. Subject to the provisions of subparagraph D below, Landlord, without
charge, except as provided herein, and in accordance with standards from time to
time prevailing for the Building, agrees: (1) to furnish running water at those
points of supply for general use of tenants of the Building; (2) to furnish to
public areas of the Building Complex heated or cooled air (as applicable),
electrical current, janitorial services, and maintenance to the extent Landlord
deems necessary; (3) to furnish, during Ordinary Business Hours, as hereinafter
defined, such heated or cooled air to the Premises standard in the downtown
Denver area, for the comfortable use and occupancy of the Premises, provided
that the recommendations of Landlord's engineer regarding occupancy and use of
the Premises are complied with by Tenant and, with respect to cooled air,
provided the same is used only for standard office use; (4) to furnish, subject
to availability and capacity of building systems, unfiltered treated cooling
tower water for use in Tenants' packaged HVAC systems, provided that such
systems are equipped with Landlord-approved strainers, pumping systems and
controls, and that such systems are connected only after approval of Landlord's
engineer; (5) to provide, during Ordinary Business Hours, the general use of
passenger elevators for ingress and egress to and from the Premises (at least
one such elevator shall be available at all times, except in the case of
emergencies or repair); (6) to provide janitorial services for the Premises to
the extent of the Building Standard tenant finish work items contained therein
(including such window washing of the outside of exterior windows as may, in the
judgment of Landlord, be reasonably required), but unless and until the Building
Standard changes, such janitorial services shall be provided after Ordinary
Business Hours on Monday through Thursday and Sunday only, except for Legal
Holidays; and (7) to cause electric current to be supplied to the Premises for
all of Tenant's Standard Electrical Usage, as hereinafter defined. "Tenant's
Standard Electrical Usage", as used herein, shall mean and refer to weekly
electrical consumption in an amount equal to multiplying three and one-half
(3.5) watts/square foot by fifty-nine (59) hours and by then multiplying the
product thereof by the number of rentable square feet in the Premises.
"Ordinary Business Hours" as used herein shall mean and refer to 7:00 a.m. to
6:00 p.m. Monday through Friday and 9:00 a.m. to 12:00 p.m. on Saturdays, Legal
Holidays excepted. "Legal Holidays," as used herein, shall mean New Year's Day,
Martin Luther King Day, Presidents' Day, Memorial Day, Independence Day, Labor
Day, Thanksgiving Day, Christmas Day, and such other national holidays as may be
hereafter established by the United States Government. Notwithstanding anything
to the contrary stated herein, Tenant shall have access to the Building 24 hours
a day, seven (7) days a week, subject to Landlord's standard security and access
procedures.

                                       8
<PAGE>   12

         B. "Excess Usage" shall be defined as any usage of electricity (1)
during other than Ordinary Business Hours; or (2) in an amount in excess of
Tenant's Standard Electrical Usage; or (3) for "Special Equipment"; or (4) for
any requirement for standard HVAC services during other than Ordinary Business
Hours. "Special Equipment", as used herein, shall mean (a) any equipment
consuming more than 0.5 kilowatts at rated capacity, (b) any equipment requiring
a voltage other than 120 volts, single phase, or (c) equipment that requires the
use of self-contained HVAC units. Tenant shall reimburse Landlord for actual
costs incurred by Landlord in providing services for Excess Usage, which costs
are subject to change from time to time. Such reasonable costs will include
Landlord's costs for materials, additional wear and tear on equipment,
utilities, and labor (including fringe and overhead costs). Computation of
Landlord's cost for providing such services will be made by Landlord's engineer,
based on his engineering survey of Tenant's Excess Usage. Tenant shall also
reimburse Landlord for all costs of supplementing the Building HVAC System
and/or extending or supplementing any electrical service, as Landlord may
determine is necessary, as a result of Tenant's Excess Usage. Prior to
installation or use by Tenant of any equipment which will result in Excess Usage
or operation of the Premises for extended hours on an ongoing basis, Tenant
shall notify Landlord of such intended installation or use and obtain Landlord's
consent thereof. In addition to the foregoing, Tenant, at Tenant's option,
upon such notice or at any time thereafter, may request Landlord, at Tenant's
sole cost and expense, to install a check meter and/or flow meter to assist in
determining the cost to Landlord of Tenant's Excess Usage. If Tenant desires
electric current and/or heated or cooled air to the Premises during periods
other than Ordinary Business Hours, Landlord will use reasonable efforts to
supply the same, but at the expense of Tenant (such expense shall be reasonably
allocated on a pro rata basis among all tenants requesting and utilizing such
services during the respective periods), at Landlord's standard rate as
established by it, from time to time, for such services. Charges for HVAC
are currently $65 per hour and $15 per hour for fan circulation only however,
such charges are subject to change. Not less than twenty-four (24) hours' prior
notice shall be given by Tenant to Landlord of Tenant's desire for such
services. It is also understood and agreed that Tenant shall pay the cost of
replacing light bulbs and/or tubes and ballast used in all lighting in the
Premises other than Building Standard lighting. The electricity for the Computer
Room and for the coolers serving the Computer Room (which are to be installed on
the roof pursuant to a separate Rooftop License Agreement with Landlord) shall
be separately metered and Tenant shall pay for the actual costs of electricity
as metered upon billing by agreement with Public Service Company of Colorado
("PSCO") from time to time. Electricity for standby or backup mode operation
of desktop computers, facsimile machines and similar electronic devices (other
than equipment in the Computer Room) outside Ordinary Business Hours shall not
be considered Excess Usage.

         C. If Tenant requires janitorial services other than those required to
be provided to other tenants of the Building Complex generally, Tenant shall
separately pay for such services monthly upon billings by Landlord, or Tenant
shall, at Landlord's option, separately contract for such services with the same
company furnishing janitorial services to Landlord. Notwithstanding the
foregoing, Tenant shall have the right, subject to Landlord's prior written
consent and such rules, regulations and requirements as Landlord may impose
(including but not limited to the requirement that such janitors belong to a
trade union), to employ janitors, other than those employed by Landlord, to
perform such additional services.

         D. Tenant agrees that Landlord shall not be liable for failure to
supply any such heating, air conditioning, elevator, electrical, janitorial,
lighting or other services, or during any period Landlord is required to reduce
or curtail such services pursuant to any applicable laws, rules, or regulations,
including regulations of any utility now or hereafter in force or effect, it
being understood that Landlord may discontinue, reduce, or curtail such
services, or any of them (either temporarily or permanently), at such times as
it may be necessary by reason of accident, repairs, alterations, improvements,
strikes, lockouts, riots, acts of God, application of applicable laws, statutes,
or rules and regulations or due to any other happening beyond the control of
Landlord. In the event of any interruption, reduction, or discontinuance of
Landlord's services (either temporary or permanent), Landlord shall not be
liable for damages to person or property as a result thereof nor shall the
occurrence of any such event in any way be construed as an eviction of Tenant;
or cause or permit an abatement, reduction or setoff of rent; or operate to
release Tenant from any of Tenant's obligations hereunder.

                                       9
<PAGE>   13

         E. Tenant agrees to notify promptly the Landlord or its representative
of any accidents or defects in the Building of which Tenant becomes aware
including defects in pipes, electric wiring, and HVAC equipment. In addition,
Tenant shall provide Landlord with prompt notification of any matter or
condition which may cause injury or damage to the Building or any person or
property therein. Notwithstanding the foregoing: (i) in the event that Landlord
is unable, for reasons within Landlord's reasonable control, to supply any of
the Building's sanitary, electrical, heating, air conditioning, water, elevator,
life safety or other essential systems serving the Premises (collectively, the
"Essential Services"), and such inability of Landlord materially impairs
Tenant's ability to carry on its business in the Premises for a period of five
(5) business days, the Base Rent and Additional Rent shall be abated commencing
with the sixth (6th) business day of such material interference with Tenant's
business, based upon the extent to which such inability to supply Essential
Services materially impairs Tenant's ability to carry on its business in the
Premises. Such abatement shall continue until the Essential Services have been
restored to such extent that the lack of any remaining services no longer
materially impairs Tenant's ability to carry on its business in the Premises.
Tenant shall not be entitled to such an abatement to the extent that Landlord's
inability to supply Essential Services to Tenant is caused by Tenant, its
employees, contractors, agents, licensees or invitees.

       7. QUIET ENJOYMENT. So long as Tenant is not in default under this
Lease, Tenant shall be entitled to the quiet enjoyment and peaceful possession
of the Premises, subject to the terms and provisions of the Lease.

       8. DEPOSIT. [SEE PARAGRAPH 2 OF RIDER TO LEASE]

       9. CHARACTER OF OCCUPANCY. Tenant covenants and agrees to occupy the
Premises for the Permitted Use and for no other purpose, and to use them in a
careful, safe, and proper manner; to pay on demand for any damage to the
Premises caused by misuse or abuse thereof by Tenant, Tenant's agents or
employees, or of any other person entering upon the Premises under express or
implied invitation of Tenant. The term "Permitted Use" shall mean: general
office use for administrative, clerical, and professional office purposes,
including, customer support (the "Primary Use") and for activities ancillary
thereto, such as computer facilities (the "Ancillary Uses"), provided that
Ancillary Uses shall not be the primary use of the Leased Premises and any
other uses that are approved by Landlord, which approval shall not be
unreasonably withheld if such uses are consistent with first class general
office

                                       10
<PAGE>   14

building uses and so long as in keeping with Building's first-class quality and
allowed under zoning applicable to the Building. Tenant shall be responsible for
obtaining any approvals or Permits required for the Ancillary Uses under
Applicable Laws and the Declaration. Tenant, at Tenant's expense, shall comply
with all laws, codes, rules, and regulations of the United States, the State of
Colorado, or of the City and County of Denver ("Applicable Laws") now in effect,
or which may hereafter be in effect, which shall impose any duty upon Landlord
or Tenant with respect to the occupation or alteration of the Premises. Tenant
shall not commit waste or suffer or permit waste to be committed or permit any
nuisance on or in the Premises. Tenant agrees that it will not store, keep, use,
sell, dispose of or offer for sale in, upon or from the Premises any article or
substance which may be prohibited by any insurance policy in force from time to
time covering the Building nor shall Tenant keep, store, produce or dispose of
on, in or from the Premises or the Building any substance which may be deemed a
hazardous substance or infectious waste under any state, local or federal rule,
statute, law, regulation or ordinance as may be promulgated or amended from time
to time. Notwithstanding the foregoing or anything to the contrary contained in
this Lease, Tenant shall not be responsible for compliance with any laws, codes,
ordinances or other governmental directives where such compliance is not related
specifically to Lessee's use and occupancy of the Premises. For example, if any
governmental authority should require the Building or the Premises to be
structurally strengthened against earthquake, or should require the removal of
asbestos from the Premises and such measures are imposed as a general
requirement applicable to all tenants rather than as a condition to Tenant's
specific use or occupancy of the Premises, such work shall be performed by and
at the sole cost of Landlord (subject to Landlord's right to include such cost
in Operating Expenses).

10. MAINTENANCE, ALTERATIONS AND REENTRY BY LANDLORD.

         A. Unless otherwise expressly provided herein, Landlord shall not be
required to make any improvements or repairs of any kind or character to the
Premises during the Primary Lease Term, or any extension thereof, except: (i)
such repairs to HVAC, mechanical, life safety and electrical systems in the
Premises (to the extent such systems are Building Standard) as may be deemed
necessary by Landlord for normal maintenance operations of the Building Complex;
and (ii) upkeep, maintenance, and repairs to all Common Areas in the Building
Complex so long as the need for any such repair is not the result of Tenant's
negligence.

         B. Tenant covenants and agrees to permit Landlord at any time to enter
the Premises after reasonable prior notice (except in the case of janitorial
services or an emergency when no notice is required) to examine and inspect the
same or, if Landlord so elects, to perform any obligations of Tenant hereunder
which Tenant shall fail to perform or to perform such cleaning, maintenance,
janitorial services, repairs, additions, or alterations as Landlord may deem
necessary or proper for the safety, improvement, or preservation of the Premises
or of other portions of the Building Complex or as may be required by
governmental authorities through any code, rule, regulation, ordinance, and/or
law. Any such reentry shall not constitute an eviction or entitle Tenant to
abatement of rent. Furthermore, Landlord shall at all times have the right at
Landlord's election to make such alterations or changes in other portions of the
Building Complex as Landlord may from time to time deem necessary and desirable
as long as such alterations and changes do not unreasonably interfere with
Tenant's use and occupancy of the Premises. Landlord may use one or more of the
street entrances to the Building Complex and such public areas thereof as may be
necessary, in Landlord's determination to complete such alterations or changes.

11. ALTERATIONS AND REPAIRS BY TENANT. [SEE RIDER]

         A. Tenant covenants and agrees not to make any Alterations in or
additions to the Premises (subsequent to the work in the Premises performed by
Landlord pursuant to the Work Letter), including installation of any equipment
or machinery therein which requires modification of or additions to any existing
electrical outlet or which would increase Tenant's usage of electricity beyond
Tenant's Standard Electrical Usage (all such alterations are referred to herein
collectively as "Alterations") without in each such instance first obtaining the
written consent of Landlord which consent shall not be unreasonably withheld so
long as the Alteration does not adversely affect any base building systems or
structural portions of the Building. No consent shall be required to the extent
such Alterations are cosmetic in nature and cost less than $25,000.00 for each

                                       11
<PAGE>   15

such Alteration; however, in any event, Landlord's consent shall be required
for any electrical, telephone or telecommunications connections or
installations outside the Premises. Landlord's consent to any Alterations by
Tenant or Landlord's approval of the plans, specifications and working drawings
for Tenant's Alterations shall create no responsibility or liability on the part
of Landlord for their completeness, design sufficiency, or compliance with all
laws, rules and regulations of governmental agencies or authorities now in
effect or which may hereafter be in effect. If expressly requested by Tenant at
the time Landlord consents to any Alteration, Landlord shall inform Tenant as
to whether Landlord will require Tenant to remove such alteration at the
expiration or earlier termination of the Lease. Tenant, at its expense, shall
pay all reasonable engineering and design costs incurred by Landlord
attributable to the Alterations and obtain all necessary, governmental permits
and certificates required for any Alterations to which Landlord has consented
and shall cause such alterations to be completed in compliance therewith and
with all applicable laws and requirements of public authorities and all
applicable requirements of Landlord's insurance carriers. All Alterations which
Tenant is permitted to make shall be performed in a good and workmanlike manner,
using new materials and equipment at least equal in quality to the original
installations in the Premises. All repair and maintenance work required to be
performed by Tenant pursuant to the provisions of subparagraph B below and any
Alterations permitted by Landlord pursuant to the provisions hereof, including,
but not limited to, any installations desired by Tenant for Tenant's
telegraphic, telephonic or electrical connections, shall be done at Tenant's
expense by Landlord's employees or, with Landlord's consent, by persons
requested by Tenant and authorized in writing by Landlord; provided, however if
such work is performed by persons who are not employees of Landlord, Tenant
shall pay to Landlord, upon receipt of billing therefor, the reasonable costs
for supervision and control of such persons as Landlord may determine to be
necessary. If Landlord authorizes persons requested by Tenant to perform such
work, prior to the commencement of any such work, on request, Tenant shall
deliver to Landlord certificates issued by insurance companies qualified to do
business in the State of Colorado, evidencing that workmen's compensation,
public liability insurance, and property damage insurance, all in the amounts,
with companies and on forms satisfactory to Landlord, are in force and effect
and maintained by all contractors and subcontractors engaged by Tenant to
perform such work. All such policies shall name Landlord and any Mortgagee (as
defined in Paragraph 20) as an additional insured. Each such certificate shall
provide that the same may not be canceled or modified without thirty (30)
days' prior written notice to Landlord and such Mortgagee. Further, Landlord
and such Mortgagee shall have the right to post notices in the Premises in
locations which will be visible by parties performing any work on the Premises
stating that Landlord is not responsible for the payment for such work and
setting forth such other information as Landlord may deem necessary.
Alterations, repair, and maintenance work shall be performed in a manner which
will not unreasonably interfere with, delay, or impose any additional expense
upon Landlord in the maintenance or operation of the Building or upon other
tenants' use of their premises.

         B. Tenant shall keep the Premises in as good order, condition, and
repair and in an orderly state, as when they were entered upon, loss by fire or
other casualty or ordinary wear excepted. Subject to Landlord's obligation to
make repairs in the event of certain casualties, as set forth in Paragraph 17
below, and except as otherwise set forth herein Landlord shall have no
obligation for the repair or replacement of any portion of the interior of the
Premises which is damaged or wears out during the term hereof regardless of the
cause therefor, including but not limited to, carpeting, draperies, window
coverings, wall coverings, painting or any of Tenant's property or betterments
in the Premises. Landlord hereby agrees that Tenant shall have the right, at its
discretion, to hypothecate Tenant's trade fixtures, equipment and other personal
property within the Premises as security for its obligation under any equipment
lease or other financing arrangement related to the conduct of Tenant's
business.

         C. All Alterations and permanent fixtures installed in the Premises
(other than Tenant's Trade Fixtures (defined below) and personal property),
including, by way of illustration and not by limitation, all partitions,
paneling, carpeting, drapes or other window coverings, and light fixtures (but
not including movable office furniture not attached to the Building and modular
furniture), shall be deemed a part of the real estate and the property of
Landlord and shall remain upon and be surrendered with the Premises as a part
thereof without molestation, disturbance, or injury at the end of the Primary
Lease Term, or any extension thereof, whether by lapse of time or otherwise,
unless Landlord by notice given to Tenant no later than fifteen (15) days prior

                                       12
<PAGE>   16

to the end of the term or as provided in Paragraph 11.A above, shall elect to
have Tenant remove all or any of the Alterations, and in such event, Tenant
shall promptly remove at Tenant's expense the Alterations specified by Landlord
and restore the Premises to their condition prior to the making of the same,
reasonable wear and tear excepted. The term "Tenant's Trade Fixtures" shall
mean, without limitation, all racking, uninterruptible power supplies (UPS)
and other computer equipment, chillers and generators installed by Tenant.

12. MECHANICS' LIENS. Tenant shall pay or cause to be paid all costs for work
done by Tenant or caused to be done by Tenant on the Premises (including work
performed by Landlord or its contractor at Tenant's request following the
commencement of the Primary Lease Term) of a character which will or may result
in liens on Landlord's interest therein and Tenant will keep the Premises free
and clear of all mechanics' liens, and other liens on account of work done for
Tenant or persons claiming under it, excluding any Tenant Finish Work
performed by Landlord pursuant to the Work Letter. Tenant hereby agrees to
indemnify, defend, and save Landlord harmless of and from all liability, loss,
damage, costs, or expenses, including attorneys' fees, on account of any claims
of any nature whatsoever including claims or liens of laborers or materialmen
or others for work performed for or materials or supplies furnished to Tenant
or persons claiming under Tenant. Should any liens be filed or recorded
against the Premises or any action affecting the title thereto be commenced as
a result of such work (which term includes the supplying of materials), Tenant
shall cause such liens to be removed of record within ten (10) days after
notice from Landlord. If Tenant desires to contest any claim of lien, Tenant
shall furnish to Landlord adequate security (which may be in the form of a
bond) of at least one hundred fifty percent (150%) of the amount of the claim,
plus estimated costs and interest and, if a final judgment establishing the
validity or existence of any lien for any amount is entered, Tenant shall pay
and satisfy the same at once. If Tenant shall be in default of the foregoing or
suit to foreclose the lien has been recorded or filed and shall not have given
Landlord security as aforesaid, Landlord may (but without being required to do
so) pay such lien or claim and any costs, and the amount so paid, together with
reasonable attorney's fees incurred in connection therewith, shall be
immediately due from Tenant to Landlord.

13. SUBLETTING AND ASSIGNMENT. [SEE PARAGRAPH 3 OF RIDER TO LEASE]

         A. Tenant shall neither sublet any part of the Premises nor assign this
Lease or any interest herein without the written consent of Landlord first being
obtained, which consent, as to any subletting of less than twenty-five percent
(25%) of the Premises, will not be unreasonably withheld provided that: (1)
Tenant has complied with the provision of subparagraph D below and Landlord has
declined to exercise its rights thereunder; (2) the proposed subtenant or
assignee is engaged in a business and the Premises will be used in a manner
which is in keeping with the then standards of the Building and does not
conflict with any exclusive use rights granted to any other tenant; (3) the
proposed subtenant or assignee has a reputation and standing in the business
community consistent with the image of tenants in a first-class office building
and has reasonable financial worth in light of the responsibilities involved and
Tenant shall have provided Landlord with reasonable proof thereof; (4) Tenant is
not in default hereunder at the time it makes its request for such consent; (5)
the proposed subtenant or assignee is not a governmental or quasi-governmental
agency; (6) the proposed subtenant or assignee is not a tenant under, or is not
currently negotiating, a lease with Landlord in the Building or in the building
located at 633 Seventeenth Street owned by Landlord; (7) the rent under such
sublease or assignment is not less than the rent to be paid by Tenant for such
space under the Lease and is not less than 85% of the rental rate then being
offered by Landlord for similar space in the Building; or (8) such subletting or
assignment does not result in a violation or create a prohibited transaction
under ERISA (as defined herein). Notwithstanding anything contained herein to
the contrary, Tenant acknowledges that if the use of the Premises by any
proposed subtenant or assignee would require compliance by Landlord and the
Building with any current or future laws to a greater extent than that required
prior to the proposed occupancy by such subtenant or assignee, Landlord, at its
sole option, may refuse to grant such consent, unless, as an express condition
thereof, Tenant and/or such assignee or subtenant bears the entire cost of such
greater compliance.

         B. If this Lease is assigned, or if the Premises or any part thereof is
sublet or occupied by anybody other than Tenant, Landlord may, after an Event of
Default by Tenant, collect the rent from the assignee, subtenant, or occupant

                                       13
<PAGE>   17

and apply the net amount collected to the rent herein reserved, but no such
assignment, subletting, occupancy, or collection shall be deemed an acceptance
of the assignee, subtenant, or occupant as the Tenant hereof or a release of
Tenant from further performance by Tenant of covenants on the part of Tenant
herein contained. A sale by Tenant of all or substantially all of its assets or
all or substantially all of its stock if Tenant is a publicly traded
corporation, a merger of Tenant with another corporation, the transfer of
twenty-five percent (25%) or more of the stock in a corporate tenant whose stock
is not publicly traded, or transfer of twenty-five percent (25%) or more of the
beneficial ownership interests in a partnership tenant shall constitute a
prohibited assignment hereunder. Consent by Landlord to any one Assignment or
sublease shall not in any way be construed as relieving Tenant from obtaining
the Landlord's express written consent to any further Assignment or sublease.
Notwithstanding the consent of Landlord to any sublease or Assignment, Tenant
shall not be relieved from its primary obligations hereunder to Landlord,
including, but not limited to the payment of all Base Rent and Tenant's Pro Rata
Share of increases in Operating Expenses. Landlord's consent to any requested
sublease or Assignment shall not waive Landlord's right to refuse to consent to
any other such request or to terminate this Lease if such request is made, all
as provided herein. If Tenant collects any rental or other amounts from a
subtenant or assignee in excess of the Base Rent and Tenant's Pro Rata Share of
increases in Operating Expenses for any monthly period, and reasonable leasing
commissions, and the unamortized value of the tenant improvements paid for by
Tenant in connection with such subletting or assignment. Tenant shall pay to
Landlord on a monthly basis, as and when Tenant receives the same, 50% of such
excess amounts received by Tenant.

         C. Notwithstanding anything contained in this Paragraph 13 to the
contrary, in the event Tenant requests Landlord's consent to sublet twenty-five
percent (25%) or more of the Premises or to assign twenty-five percent (25%) or
more of its interest in this Lease for all or substantially all of the remainder
of the Primary Lease Term (or the current Option Term, as applicable), Landlord
shall have the right to (1) consent to such sublease or Assignment in its
reasonable discretion; (2) refuse to grant such consent in Landlord's reasonable
discretion; or (3) refuse to grant such consent and terminate this Lease as to
the portion of the Premises with respect to which such consent was requested;
provided, however, if Landlord refuses to grant such consent and elects to
terminate the Lease as to such portion of the Premises, Tenant shall have the
right within fifteen (15) days after notice of Landlord's exercise of its right
to terminate to withdraw Tenant's request for such consent and remain in
possession of the Premises under the terms and conditions hereof. In the event
the Lease is terminated as set forth herein, such termination shall be effective
as of the effective date of the proposed Assignment or subletting and Landlord
shall make alterations to the extent necessary to create demising walls
separating the terminated space from the remainder of the Premises.

         D. Tenant hereby agrees that in the event it desires to sublease all or
any portion of the Premises or assign this Lease to any party, in whole or in
part, (herein "Assignment"), Tenant shall notify Landlord not less than sixty
(60) days prior to the date Tenant desires to sublease such portion of the
Premises or assign this Lease ("Tenant's Notice"). Tenant's Notice shall set
forth the description of the portion of the Premises to be so sublet or assigned
and the terms and conditions on which Tenant desires to sublet the Premises or
assign this Lease. Landlord shall have thirty (30) days following receipt of
Tenants Notice to respond pursuant to Paragraph 13C above.

                                       14

<PAGE>   18

         E. All documents utilized by Tenant to evidence any subletting or
assignment to which Landlord has consented shall be subject to prior approval by
Landlord or its counsel. Tenant shall pay on demand all of Landlord's costs and
expenses, including reasonable attorneys' fees, incurred in determining whether
or not to consent to any requested sublease or Assignment and in reviewing and
approving such documentation.

         F. Landlord and Tenant understand that notwithstanding certain
provisions to the contrary contained herein, a trustee or debtor in possession
under the Bankruptcy Code of the United States may have certain rights to assume
or assign this Lease. If a trustee in bankruptcy is entitled to assume control
over Tenant's rights under this Lease and assigns such rights to any third
party, the Base Rent to be paid hereunder by such party shall be increased to
the then current Base Rent (if greater than then being paid for the Premises)
which Landlord would charge for comparable space in the Building as of the date
of such third party's occupancy of the Premises. Landlord and Tenant further
understand that in any event Landlord is entitled under the Bankruptcy Code to
Adequate Assurance of future performance of the terms and provisions of this
Lease. For purposes of any such assumption or assignment, the parties hereto
agree that the term "Adequate Assurance" shall include at least the following:

               (1) In order to assure Landlord that the proposed assignee will
have the resources with which to pay the rent called for herein, any proposed
assignee must have as demonstrated to Landlord's satisfaction a net worth (as
defined in accordance with generally accepted accounting principles consistently
applied) at least as great as the net worth of Tenant on the date this Lease
became effective increased by seven percent (7%), compounded annually, for each
year from the Lease Commencement Date through the date of the proposed
assignment. The financial condition and resources of Tenant were a material
inducement to Landlord in entering into this Lease.

               (2) Any proposed assignee of this Lease must assume and agree
to be personally bound by the terms, provisions, and covenants of this Lease.

14. DAMAGE TO PROPERTY. Tenant shall neither hold nor attempt to hold Landlord
liable for any injury or damage, either proximate or remote, occurring through
or caused by fire, water, steam, or any repairs, alterations, injury, accident,
or any other cause to the Premises, to any furniture, fixtures, Tenant
improvements, or other personal property of Tenant kept or stored in the
Premises, or in other parts of the Building Complex not herein demised, whether
by reason of the negligence or default of the owners or occupants thereof or any
other person or otherwise and the keeping or storing of all property of Tenant
in the Building Complex and/or Premises shall be at the sole risk of Tenant.
Tenant shall obtain and maintain throughout the term of this Lease "all risk" or
"multi-peril" insurance on and for the full cost of replacement of all of
Tenant's property and betterments in the Premises, including, without limitation
all furniture, fixtures, personal property and all tenant finish in excess of
Building Standard items. Any proceeds from such insurance shall be payable to
Tenant.

15. INDEMNITY TO LANDLORD.

         A. Tenant hereby agrees to indemnify, defend, and save Landlord
harmless of and from all liability, loss, damages, costs, or expenses, including
attorneys' fees, on account of injuries to the person or property of Landlord or
of any other tenant in the Building Complex or to any other person rightfully in
said Building Complex for any purpose whatsoever, where the injuries are caused
by the negligence, misconduct or breach of this Lease by the Tenant, Tenant's
agent's, servants, or employees or of any other person entering upon the
Premises under express or implied invitation of Tenant or where such injuries
are the result of the violation of the provisions of this Lease by any of such
persons. This indemnity shall survive termination or earlier expiration of this
Lease.

         B. In addition to the above, Tenant shall obtain and maintain
throughout the term of this Lease a commercial general liability policy,

                                       15

<PAGE>   19

including protection against death, personal injury and property damage, issued
by an insurance company qualified to do business in the State of Colorado with
an AM Best rating of no less than A-, VII, with a single limit of not less
than One Million Dollars (1,000,000.00). All such policies shall name Landlord
as an additional insured. Each such policy shall provide that the same may not
be canceled or modified without at least twenty (20) days' prior written
notice to Landlord and any Mortgagee (as defined in Paragraph 20). Prior to
occupancy of the Premises, and thereafter from time to time, Tenant shall
deliver certificates evidencing that such insurance, as required under Paragraph
14 above and this Paragraph 15, is in force and effect. The limits of said
insurance shall not, under any circumstances, limit the liability of Tenant
hereunder.

16. SURRENDER AND NOTICE. Upon the expiration or other termination of the term
of this Lease, Tenant shall promptly quit and surrender to Landlord the Premises
broom clean, in good order and condition, ordinary wear and tear and loss by
fire or other casualty or condemnation excepted unless due to the negligence of
Tenant (and not covered by insurance), and Tenant shall remove all of its
movable furniture and other effects and such Alterations, as Landlord may be
entitled to require Tenant to remove pursuant to Paragraph 11 hereof. In the
event Tenant fails to vacate the Premises on a timely basis as required, Tenant
shall be responsible to Landlord for all costs incurred by Landlord as a result
of such failure, including, but not limited to, any amounts required to be paid
to third parties who were to have occupied the Premises.

17. INSURANCE, CASUALTY, AND RESTORATION OF PREMISES.

         A. Landlord shall maintain casualty insurance on the shell and core of
the Building, on the Premises to the extent of the base tenant finish per the
then-current standard allowance provided by Landlord to tenants in the Building
therein and in the Building Complex, in such amounts, from such companies, and
on such terms and conditions, including loss of rental insurance for such period
of time as Landlord deems appropriate, from time to time.

         B. If the Premises or the Building shall be so damaged by fire or other
casualty as to render the Premises wholly untenantable and if such damage shall
be so great that a competent architect, in good standing, selected by Landlord
shall certify in writing to Landlord and Tenant within sixty (60) days of said
casualty that the Premises, with the exercise of reasonable diligence, cannot be
made fit for occupancy within one hundred eighty (180) working days from the
happening thereof, then this Lease shall cease and terminate from the date of
the occurrence of such damage and Tenant shall thereupon surrender to Landlord
the Premises and all interest therein hereunder and Landlord may reenter and
take possession of the Premises and remove Tenant therefrom. Tenant shall pay
rent, duly apportioned, up to the time of such termination of this Lease. If,
however, the damage shall be such that said architect shall certify within said
sixty (60) day period that the Premises can be made tenantable within said one
hundred eighty (180) day period, then, except as hereinafter provided, Landlord
shall repair the damage so done (to the extent of the base tenant finish per the
then-current standard allowance provided by Landlord to tenants in the Building)
with all reasonable speed.

         C. If the Premises shall be slightly damaged by fire or other casualty,
but not so as to render the same wholly untenantable or to require a repair
period in excess of one hundred eighty (180) days, then, Landlord, after
receiving notice in writing of the occurrence of the casualty, except as
hereafter provided, shall cause the same to be repaired to the extent of the
base tenant finish per the then-current standard allowance provided by Landlord
to tenants in the Building with reasonable promptness. If the estimated repair
period as established in accordance with the provisions of subparagraph B above
exceeds one hundred eighty (180) days, then the provisions of subparagraph B
shall control notwithstanding the fact that the Premises are not wholly
untenantable.

         D. In case the Building throughout shall be so injured or damaged,
whether by fire or otherwise (though said Premises may not be affected, or if
affected, can be repaired within said one hundred eighty (180) days), that,
within sixty (60) days after the happening of such injury, Landlord shall decide
not to reconstruct or rebuild said Building, then, notwithstanding anything
contained herein to the contrary, upon notice in writing to that effect given by
Landlord to Tenant within said sixty (60) days, Tenant shall pay the rent,
properly apportioned up to such date, this Lease shall terminate from the date

                                       16
<PAGE>   20

of delivery of said written notice, and both parties hereto shall be freed and
discharged of all further obligations hereunder.

         E. Landlord and Tenant hereby waive any and all rights of recovery
against the other, their officers, agents, and employees occurring out of the
use and occupancy of the Premises for loss or damage to their respective real
and/or personal property arising as a result of a casualty or condemnation
contemplated by this Paragraph 17. Each of the parties shall, upon obtaining the
policies of insurance required by this Lease, notify the insurance carrier that
the foregoing waiver is contained in this Lease and shall require such carrier
to include an appropriate waiver of subrogation provision in the policies.

         F. Provided that the casualty is not the fault of Tenant, Tenant's
agents, servants, or employees, Tenant's rent shall abate during any such period
of repair and restoration, but only to the extent of any recovery by Landlord
under its rental insurance related to the Premises in the same proportion that
the part of the Premises rendered untenantable bears to the whole.

18. CONDEMNATION. If the entire Premises or substantially all of the Premises or
any portion of the Building Complex which shall render the Premises untenantable
shall be taken by right of eminent domain or by condemnation or shall be
conveyed in lieu of any such taking, then this Lease, at the option of either
Landlord or Tenant exercised by either party giving notice to the other of such
termination within thirty (30) days after such taking or conveyance, shall
forthwith cease and terminate and the rent shall be duly apportioned as of the
date of such taking or conveyance. Tenant thereupon shall surrender the Premises
and all interest therein under this Lease to Landlord and Landlord may reenter
and take possession of the Premises or remove Tenant therefrom. In the event
less than all of the Premises shall be taken by such proceeding, Landlord shall
promptly repair the Premises as nearly as possible to its condition immediately
prior to said taking, unless Landlord elects not to reconstruct or rebuild as
described in subparagraph D of Paragraph 17 above. In the event of any such
taking or conveyance, Landlord shall receive the entire award or consideration
for the portion of the Building so taken.

19. DEFAULT BY TENANT.

         A. Each one of the following events is herein referred to as an "Event
of Default":

               (1) Any failure by Tenant to pay the rent or any other monetary
sums required to be paid hereunder on the date such sums are due shall be deemed
as default. Notwithstanding the foregoing, Tenant may cure a default under this
provision at any time prior to five (5) business days after written notice of
such default is given by Landlord exercising its remedies as to such default
under this Lease; provided, however, Tenant shall not be entitled to more than
two (2) notices of a delinquency in payment during any calendar year and, if
thereafter during such calendar year any rent or other amounts owing hereunder
are not paid when due, an Event of Default shall be deemed to have occurred
immediately even though no notice thereof is given;

               (2) Tenant shall abandon the Premises;

               (3) This Lease or the estate of Tenant hereunder shall be
transferred to or shall pass to or devolve upon any other person or party in
violation of the provisions set forth in Paragraph 13;

               (4) This Lease or the Premises or any part thereof shall be taken
upon execution or by other process of law directed against Tenant or shall be
taken upon or subject to any attachment at the instance of any creditor of or
claimant against Tenant and said attachment shall not be discharged or disposed
of within fifteen (15) days after the levy thereof;

               (5) The filing of any petition or the commencement of any case or
proceeding by the Tenant under any provision or chapter of the Federal
Bankruptcy Act, the Federal Bankruptcy Code, or any other federal or state law
relating to insolvency, bankruptcy, or reorganization or the adjudication that
the Tenant is insolvent or bankrupt or the entry of an order for relief under
the Federal Bankruptcy Code with respect to Tenant;

               (6) The filing of any petition or the commencement of any case
or proceeding described in subparagraph (5) above against the Tenant, unless
such

                                       17
<PAGE>   21

petition and all proceedings initiated thereby are dismissed within sixty (60)
days from the date of such filing; the filing of an answer by Tenant admitting
the allegations of any such petition; the appointment of or taking possession by
a custodian, trustee or receiver for all or any assets of the Tenant, unless
such appointment is vacated or dismissed within sixty (60) days from the date of
such appointment;

               (7) The insolvency of the Tenant or the execution by the Tenant
of an assignment for the benefit of creditors; the convening by Tenant of a
meeting of its creditors, or any class thereof, for purposes of effecting a
moratorium upon or extension or composition of its debts; or the failure of the
Tenant generally to pay its debts as they mature;

               (8) The admission in writing by Tenant, or any partner of Tenant
if Tenant is a partnership, that he is unable to pay his debts as they mature or
he is generally not paying his debts as they mature;

               (9) [Intentionally Deleted]

               (10) Tenant shall fail to perform any of the other agreements
terms, covenants, or conditions hereof on Tenant's part to be performed and such
non-performance shall continue for a period of thirty (30) days after written
notice thereof by Landlord to Tenant or, if such performance cannot be
reasonably had within such thirty (30) day period, Tenant shall not in good
faith have commenced such performance within such thirty (30) day period and
shall not diligently proceed therewith to completion; provided, however, if
Tenant fails to perform any of the other agreements, covenants or conditions
hereof repeatedly during the term of this Lease, Tenant shall no longer have the
opportunity to cure any subsequent failure and an Event of Default shall be
deemed to have occurred immediately upon such failure.

         B. Remedies of Landlord. If any one or more Event of Default shall
happen, then Landlord shall have the right at Landlord's election, then or at
any time thereafter, either:

               (1) (a) Without demand or notice, to reenter and take possession
of the Premises or any part thereof and repossess the same as of Landlord's
former estate and expel Tenant and those claiming through or under Tenant and
remove the effects of both or either, without being deemed guilty of any manner
of trespass and without prejudice to any remedies for arrears of rent or
preceding breach of covenants or conditions. Should Landlord elect to reenter,
as provided in this subparagraph (1), or should Landlord take possession
pursuant to legal proceedings or pursuant to any notice provided for by law,
Landlord may, from time to time, without terminating this Lease, relet the
Premises or any part thereof, either alone or in conjunction with other
portions of the Building of which the Premises are a part, in Landlord's or
Tenant's name but for the account of Tenant, for such term or terms (which may
be greater or less than the period which would otherwise have constituted the
balance of the term of this Lease) and on such conditions and upon such other
terms (which may include concessions of free rent and alteration and repair of
the Premises) as Landlord, in its uncontrolled discretion, may determine and
Landlord may collect and receive the rents therefor. Landlord shall in no way
be responsible or liable for any failure to relet the Premises, or any part
thereof, or for any failure to collect any rent due upon such reletting but
Landlord shall use reasonable efforts to mitigate damages caused by Tenants'
default, but Landlord shall have the right to Lease other vacant space in the
Building Complex in preference to leasing the Premises. No such reentry or
taking possession of the Premises by Landlord shall be construed as an election
on Landlord's part to terminate this Lease unless a written notice of such
intention be given to Tenant. No notice from Landlord hereunder or under a
forcible entry and detainer statute or similar law shall constitute an election
by Landlord to terminate this Lease unless such notice specifically so states.
Landlord reserves the right following any such reentry and/or reletting to
exercise its right to terminate this Lease by giving Tenant such written
notice, in which event the Lease will terminate as specified in said notice.

               (b) If Landlord elects to take possession of the Premises as
provided in this subparagraph (1) without terminating the Lease, Tenant shall
pay to Landlord (i) the rent and other sums as herein provided, which would be
payable hereunder if such repossession had not occurred, less (ii) the net
proceeds, if any, of any reletting of the Premises after deducting all of

                                       18
<PAGE>   22

Landlord's expenses incurred in connection with such reletting, including, but
without limitation, all repossession costs, brokerage commissions, legal
expenses, attorneys' fees, expenses of employees, alteration, remodeling, and
repair costs and expenses of preparation for such reletting. If, in connection
with any reletting, the new lease term extends beyond the existing term or the
premises covered thereby include other premises not part of the Premises, a fair
apportionment of the rent received from such reletting and the expenses
incurred in connection therewith, as provided aforesaid, will be made in
determining the net proceeds received from such reletting. In addition, in
determining the net proceeds from such reletting, any rent concessions will be
apportioned over the term of the new lease. Tenant shall pay such amounts to
Landlord monthly on the days on which the rent and all other amounts owing
hereunder would have been payable if possession had not been retaken and
Landlord shall be entitled to receive the same from Tenant on each such day; or

               (2) To give Tenant written notice of intention to terminate this
Lease on the date of such given notice or on any later date specified therein
and, on the date specified in such notice, Tenant's right to possession of the
Premises shall cease and the Lease shall thereupon be terminated, except as to
Tenant's liability hereunder as hereinafter provided, as if the expiration of
the term fixed in such notice were the end of the term herein originally
demised. In the event this Lease is terminated pursuant to the provisions of
this subparagraph (2), Tenant shall remain liable to Landlord for damages in an
amount equal to the rent and other sums which would have been owing by Tenant
hereunder for the balance of the term had this Lease not been terminated less
the net proceeds, if any, of any reletting of the Premises by Landlord
subsequent to such termination, after deducting all Landlord's expenses in
connection with such reletting, including, but without limitation, the expenses
enumerated above. Landlord shall be entitled to collect such damages from Tenant
monthly on the days on which the rent and other amounts would have been payable
hereunder if this Lease had not been terminated and Landlord shall be entitled
to receive the same from Tenant on each such day. Alternatively, at the option
of Landlord, in the event this Lease is terminated, Landlord shall be entitled
to recover forthwith against Tenant as damages for loss of the bargain and not
as a penalty an amount equal to the worth at the time of termination of the
excess, if any, of the amount of rent reserved in this Lease for the balance of
the term hereof over the then Reasonable Rental Value of the Premises for the
same period plus all amounts incurred by Landlord in order to obtain possession
of the Premises and relet the same, including attorneys' fees, reletting
expenses, alterations and repair costs, brokerage commissions and all other like
amounts. It is agreed that the "Reasonable Rental Value" shall be the amount of
rental which Landlord can obtain as rent for the remaining balance of the term.

         C. Cumulative Remedies. Suit or suits for the recovery of the rents and
other amounts and damages set forth hereinabove may be brought by Landlord, from
time to time, at Landlord's election, and nothing herein shall be deemed to
require Landlord to await the date whereon this Lease or the term hereof would
have expired had there been no such default by Tenant or no such termination, as
the case may be. Each right and remedy provided for in this Lease shall be
cumulative and shall be in addition to every other right or remedy provided for
in this Lease or now or hereafter existing at law or in equity or by statute or
otherwise, including, but not limited to, suits for injunctive relief and
specific performance. The exercise or beginning of the exercise by Landlord of
any one or more of the rights or remedies provided for in this Lease or now or
hereafter existing at law or in equity or by statute or otherwise shall not
preclude the simultaneous or later exercise by Landlord of any or all other
rights or remedies provided for in this Lease or now or hereafter existing at
law or in equity or by statute or otherwise. All such rights and remedies shall
be considered cumulative and non-exclusive. All costs incurred by Landlord in
connection with collecting any rent or other amount and damages owing by Tenant
pursuant to the provisions of this Lease, or to enforce any provision of this
Lease, shall also be recoverable by Landlord from Tenant. Further, if an action
is brought pursuant to the terms and provisions of the Lease, the prevailing
party in such action shall be entitled to recover from the other party any and
all reasonable attorneys' fees incurred by such prevailing party in connection
with such action.

         D. No Waiver. No failure by Landlord to insist upon the strict
performance of any agreement, term, covenant or condition hereof or to exercise
any right or remedy consequent upon a breach thereof and no acceptance of full
or partial rent during the continuance of any such breach shall constitute a
waiver of any such breach or of such agreement, term, covenant, or condition.

                                       19
<PAGE>   23

No agreement, term, covenant, or condition hereof to be performed or complied
with by Tenant and no breach thereof shall be waived, altered, or modified,
except by written instrument executed by Landlord. No waiver of any breach shall
affect or alter this Lease but each and every agreement, term, covenant, and
condition hereof shall continue in full force and effect with respect to any
other then existing or subsequent breach thereof. Notwithstanding any
termination of this Lease, the same shall continue in force and effect as to any
provisions which require observance or performance by Landlord or Tenant
subsequent to such termination.

         E. Bankruptcy. Nothing contained in this Paragraph 19 shall limit or
prejudice the right of Landlord to prove and obtain as liquidated damages in any
bankruptcy, insolvency, receivership, reorganization, or dissolution proceeding
an amount equal to the maximum allowed by any statute or rule of law governing
such a proceeding and in effect at the time when such damages are to be proved,
whether or not such amount be greater, equal to, or less than the amounts
recoverable, either as damages or rent, referred to in any of the preceding
provisions of this Paragraph. Notwithstanding anything contained in this
Paragraph to the contrary, any such proceeding or action involving bankruptcy,
insolvency, reorganization, arrangement, assignment for the benefit of
creditors, or appointment of a receiver or trustee, as set forth above, shall be
considered to be an Event of Default only when such proceeding, action, or
remedy shall be taken or brought by or against the then holder of the leasehold
estate under this Lease.

         F. Late Payment Charge. Any rents or other amounts owing hereunder
which are not paid within five (5) days after the date they are due shall
thereafter bear interest at the rate of three percentage points over the Prime
Rate then being charged by Wells Fargo Bank, N.A., or its successor, to its most
credit-worthy customers on an unsecured basis for short term loans (the "Prime
Rate") or the highest rate permitted by applicable usury law, whichever is
lower, until paid. Further, in the event any rents or other amounts owing
hereunder are not paid within five (5) days after written notice, Landlord and
Tenant agree that Landlord will incur additional administrative expenses, the
amount of which will be difficult if not impossible to determine. Accordingly,
Tenant shall pay to Landlord an additional, one-time late charge for any such
late payment in the amount of five percent (5%) of such payment. Any amounts
paid by Landlord to cure any defaults of Tenant hereunder, which Landlord shall
have the right but not the obligation to do, shall, if not repaid by Tenant
within five (5) days of demand by Landlord, thereafter bear interest at the rate
of three percentage points over the Prime Rate or the highest rate permitted by
applicable usury law, whichever is lower, until paid.

         G. Waiver of Jury Trial. Tenant and Landlord hereby waive (to the
extent allowed by law) any and all rights to a trial by jury in suit or suits
brought to enforce any provision of this Lease or arising out of or concerning
the provisions of this Lease.

20. DEFAULT BY LANDLORD. In the event of any alleged default on the part of
Landlord hereunder, Tenant shall give written notice to Landlord in the manner
herein set forth and shall afford Landlord a reasonable opportunity to cure any
such default. Notice to Landlord of any such alleged default shall be
ineffective unless notice is simultaneously delivered to any holder of a
Mortgage and/or Trust Deed affecting all or any portion of the Building Complex
("Mortgagees"), as hereafter provided. Tenant agrees to give all Mortgagees, by
certified mail, return receipt requested, a copy of any notice of default served
upon Landlord, provided that prior to such notice Tenant has been notified, in
writing (by way of notice of Assignment of Rents and Leases, or otherwise), of
the address of such Mortgagees. Tenant further agrees that if Landlord shall
have failed to cure such default within the time provided for in this Lease,
then the Mortgagees shall have an additional thirty (30) days within which to
cure such default or, if such default cannot be cured within that time, then
such additional time as may be necessary, if, within such thirty (30) days, any
Mortgagee has commenced and is diligently pursuing the remedies necessary to
cure such default (including, but not limited to, commencement of foreclosure
proceedings, if necessary to effect such cure), in which event this Lease shall
not be terminated while such remedies are being so diligently pursued. In no
event will Landlord or any Mortgagee be responsible for any consequential
damages incurred by Tenant as a result of any default, including, but not
limited to, lost profits or interruption of business as a result of any alleged
default by Landlord hereunder.

                                       20

<PAGE>   24

21. SUBORDINATION AND ATTORNMENT. (SEE PARAGRAPH 4 OF RIDER TO LEASE)

         A. This Lease, at Landlord's option, shall be subordinate to any
mortgage or deed of trust (now or hereafter placed upon the Building Complex, or
any portion thereof), including any amendment, modification, or restatement of
any of such documents, and to any and all advances made under any mortgage or
deed of trust and to all renewals, modifications, consolidations, replacements,
and extensions thereof. Tenant agrees that with respect to any of the foregoing
documents, no documentation, other than this Lease, shall be required to
evidence such subordination.

         B. If any holder of a mortgage or deed of trust shall elect to have
this Lease superior to the lien of the holder's mortgage or deed of trust and
shall give written notice thereof to Tenant, this Lease shall be deemed prior to
such mortgage or deed of trust, whether this Lease is dated prior or subsequent
to the date of said mortgage or deed of trust or the date of recording thereof.

         C. In confirmation of such subordination or superior position, as the
case may be, Tenant agrees to execute such documents as may be required by
Landlord or its Mortgagee to evidence the subordination of its interest herein
to any of the documents described above, or to evidence that this Lease is prior
to the lien of any mortgage or deed of trust, as the case may be, and failing to
do so within ten (10) days after written demand, Tenant does hereby make,
constitute, and irrevocably appoint Landlord as Tenant's attorney-in-fact and in
Tenant's name, place, and stead, to do so.

         D. Tenant hereby agrees to attorn to all successor owners of the
Building Complex, whether or not such ownership is acquired as a result of a
sale, through foreclosure of a deed of trust or mortgage, or otherwise.

22. REMOVAL OF TENANT'S PROPERTY.

         A. All movable furniture and personal effects of Tenant not removed
from the Premises upon the vacation or abandonment thereof or upon the
termination of this Lease for any cause whatsoever shall conclusively be deemed
to have been abandoned and may be appropriated, sold, stored, destroyed, or
otherwise disposed of by Landlord without notice to Tenant or any other person
and without obligation to account therefor and Tenant shall pay Landlord all
expenses incurred in connection with the disposition of such property.

         B. [Intentionally Deleted]

23. HOLDING OVER: TENANCY MONTH-TO-MONTH. If, after the expiration of this
Lease, Tenant shall remain in possession of the Premises and continue to pay
rent, and Landlord shall accept such rent, without any express written agreement
as to such holding over, then such holding over shall be deemed and taken to be
a holding upon a tenancy from month-to-month, subject to all the terms and
conditions hereof on the part of Tenant to be observed and performed and at a
monthly rent equivalent to one hundred fifty percent (150%) of the monthly
installments paid by Tenant immediately prior to such expiration or the Current
Market Rental Rate for the Premises, whichever is greater. All such rent shall
be payable in advance on the same day of each calendar month. Such
month-to-month tenancy may be terminated by either party upon ten (10) days'
notice prior to the end of any such monthly period. Nothing contained herein
shall be construed as obligating Landlord to accept any rental tendered by
Tenant after the expiration of the term hereof or as relieving Tenant of its
liability pursuant to Paragraph 16 and any holdover without Landlord's consent
shall be deemed a default hereunder entitling Landlord to all of its

                                       21
<PAGE>   25

rights and remedies set forth in Paragraph 19 above, including, without
limitation, its right to recover consequential damages resulting from said
holdover.

24. PAYMENTS AFTER TERMINATION. No payments of money by Tenant to Landlord after
the termination of this Lease, in any manner, or after giving of any notice
(other than a demand for payment of money) by Landlord to Tenant shall
reinstate, continue, or extend the term of this Lease or affect any notice given
to Tenant prior to the payment of such money, it being agreed that after the
service of notice or the commencement of a suit or other final judgment granting
Landlord possession of the Premises, Landlord may receive and collect any sums
of rent due or any other sums of money due under the terms of this Lease or
otherwise exercise Landlord's rights and remedies hereunder and the payment of
such sums of money, whether as rent or otherwise; shall not waive said notice or
in any manner affect any pending suit or judgment theretofore obtained.

25. STATEMENT OF PERFORMANCE. Tenant agrees at any time and from time to time,
upon not less than ten (10) days' prior written request by Landlord, to execute,
acknowledge, and deliver to Landlord a statement in writing certifying that this
Lease is unmodified and in full force and effect (or, if there have been
modifications, that the same is in full force and effect as modified and stating
the modifications), that there have been no defaults thereunder by Landlord or
Tenant (or, if there have been defaults, setting forth the nature thereof), the
date to which the rent and other charges have been paid in advance, if any, and
such other information as Landlord may request. It is intended that any such
statement delivered pursuant to this Paragraph may be relied upon by any
prospective purchaser of all or any portion of Landlord's interest herein or a
holder of any mortgage or deed of trust encumbering the Building Complex.
Tenant's failure to deliver such statement within such time shall be conclusive
upon Tenant that: (i) this Lease is in full force and effect, without
modification except as may be represented by Landlord; (ii) there are no uncured
defaults in Landlord's performance; and (iii) not more than one (1) month's rent
has been paid in advance. Further, upon request, Tenant will supply to Landlord
a corporate or partnership resolution, as the case may be, certifying that the
party signing said statement of Tenant is properly authorized to do so.

26. MISCELLANEOUS.

         A. The term "Landlord" as used in this Lease, so far as covenants or
obligations on the part of Landlord are concerned, shall be limited to mean and
include only the owner or owners of the Building Complex at the time in question
and, in the event of any transfer or transfers of the title thereto, Landlord
herein named (and in the case of any subsequent transfers or conveyances, the
then grantor) shall be automatically released, from and after the date of such
transfer or conveyance, of all liability as respects the performance of any
covenants or obligations on the part of Landlord contained in this Lease
thereafter to be performed, provided that any funds in the hands of Landlord or
the then grantor at the time of such transfer in which Tenant has an interest
shall be turned over to the grantee and any amount then due and payable to
Tenant by Landlord or the then grantor under any provisions of this Lease shall
be paid to Tenant.

         B. The termination or mutual cancellation of this Lease shall not work
a merger, and such termination or mutual cancellation shall, at the option of
Landlord, either terminate all subleases and subtenancies or operate as an
assignment to Landlord of any or all such subleases or subtenancies.

         C. The Tenant agrees that, for the purposes of completing or making
repairs or alterations in any portion of the Building, Landlord may use one or
more of the street entrances, the halls, passageways, and elevators of the
Building.

         D. This Lease shall be construed as though the covenants herein between
Landlord and Tenant are independent and not dependent and Tenant shall not be
entitled to any setoff of the rent or other amounts owing hereunder against
Landlord if Landlord fails to perform its obligation set forth herein (except as
expressly set forth herein); provided, however, the foregoing shall in no way
impair the right of Tenant to commence a separate action against Landlord for
any violation by Landlord of the provisions hereof so long as notice is first
given to Landlord and any holder of a mortgage or deed of trust covering the
Building Complex or any portion thereof and an opportunity granted to Landlord
and such holder to correct such violation as provided in Paragraph 20 above.

                                       22

<PAGE>   26

         E. If any clause or provision of this Lease is illegal, invalid, or
unenforceable under present or future laws effective during the term of this
Lease, then and in that event it is the intention of the parties hereto that the
remainder of this Lease shall not be affected thereby and it is also the
intention of the parties to this Lease that in lieu of each clause or provision
of this Lease that is illegal, invalid, or unenforceable there be added as a
part of this Lease a clause or provision as similar in terms to such illegal,
invalid, or unenforceable clause or provision as may be possible and be legal,
valid, and enforceable.

         F. The caption of each paragraph is added as a matter of convenience
only and shall be considered of no effect in the construction of any provision
or provisions of this Lease.

         G. Except as herein specifically set forth, all terms, conditions, and
covenants to be observed and performed by the parties hereto shall be applicable
to and binding upon their respective heirs, administrators, executors, and
assigns. The terms, conditions, and covenants hereof shall also be considered to
be covenants running with the land to the fullest extent permitted by law.

         H. Tenant and the party executing this Lease on behalf of Tenant
represent to Landlord that such party is authorized to do so by requisite
action of the board of directors or partners, as the case may be, and agree,
upon request, to deliver to Landlord a resolution or similar document or opinion
of counsel to that effect.

         I. If there are more than one entity or person which or who are the
Tenant under this Lease, the obligations imposed upon Tenant under this Lease
shall be joint and several.

         J. No act or thing done by Landlord or Landlord's agents during the
term hereof, including, but not limited to, any agreement to accept surrender of
the premises or to amend or modify this Lease, shall be deemed to be binding on
Landlord, unless such act or thing shall be by a partner or officer of
Landlord, as the case may be, or a party designated in writing by Landlord as
so authorized to act. The delivery of keys to Landlord, or Landlord's agents,
employees, or officers shall not operate as a termination of this Lease or a
surrender of the Premises. No payment by Tenant or receipt by Landlord of a
lesser amount than the monthly rent and all other amounts owing, as herein
stipulated, shall be deemed to be other than on account of the earliest
stipulated rent or other amounts nor shall any endorsement or statement on any
check or any letter accompanying any check or payment as rent be deemed an
accord and satisfaction and Landlord may accept such check or payment without
prejudice to Landlord's right to recover the balance of such rent or pursue any
other remedy available to Landlord.

         K. Landlord shall have the right at any time to change the name of the
Building, to increase the size of the Building Complex by adding additional
real property thereto, to construct other buildings or improvements on any
portion of the Building Complex or to change the location and/or character of or
to make alterations of or additions to the Building Complex. In the event any
such additional buildings are constructed or Landlord increases the size of the
Building Complex, Landlord and Tenant shall execute an Amendment to Lease which
incorporates such modifications, additions, and adjustments to Tenant's Pro Rata
Share, if necessary. Tenant shall not use the Building's name for any purpose
other than as a part of its' business address. Any use of such name in the
designation of Tenant's business shall constitute a default under this Lease.

         L. Tenant covenants and agrees that no diminution of light, air, or
view of or from the Building or any other building (whether or not constructed
or owned by Landlord) shall entitle Tenant to any reduction of rent or other
charges under this Lease, result in any liability of Landlord to Tenant, or in
any way affect this Lease or Tenant's obligations hereunder.

         M. Notwithstanding anything to the contrary contained herein,
Landlord's liability under this Lease shall be limited to Landlord's interest in
the Building Complex.

         N. Tenant acknowledges and agrees that it has not relied upon any
statements, representations, agreements; or warranties by Landlord, its agents
or employees, except such as are expressed herein and that no amendment or
modification of this Lease shall be valid or binding unless expressed in writing

                                       23
<PAGE>   27

and executed by the parties hereto in the same manner as the execution of this
Lease.

         O. Tenant agrees to make such modification and amendments of this Lease
as may hereafter be required to conform to any lender's requirements, so long as
such modifications or amendments will not increase Tenant's obligations
hereunder or materially alter its rights as set forth herein.

         P. Submission of this instrument for examination or signature by Tenant
does not constitute a reservation of or an option for lease, and it is not
effective as a lease or otherwise until execution and delivery by both Landlord
and Tenant.

21. AUTHORITIES FOR ACTION AND NOTICE.

         A. Except as herein otherwise provided, Landlord may act in any manner
provided for herein by and through Landlord's Building Manager or any other
person who shall from time to time be designated in writing.

         B. All notices, demands, statements or communications required or
permitted to be given to Landlord hereunder shall be in writing and shall be
deemed duly served when delivered personally to any officer of Landlord (or a
partner of Landlord if Landlord is a partnership or to Landlord individually if
Landlord is a sole proprietor) or manager of Landlord whose principal office is
in the Building, or when deposited in the United States mail, postage prepaid,
certified or registered, return receipt requested, addressed to Landlord at
Landlord's principal office in the Building or at the most recent address of
which Landlord has notified Tenant in writing. All notices, demands, statements
or communications required to be given to Tenant hereunder shall be in writing
and shall be deemed duly served when delivered personally to any officer of
Tenant (or a partner of Tenant if Tenant is a partnership or to Tenant
individually if Tenant is a sole proprietor) or manager of Tenant whose office
is in the Building, when deposited in the United States mail, postage prepaid,
certified or registered, return receipt requested, addressed to Tenant at the
Premises, or, prior to Tenant's taking possession of the Premises, to the
address known to Landlord as Tenant's principal office address. Either party
shall have the right to designate in writing, served as above provided, a
different address to which notice is to be mailed. The foregoing shall in no
event prohibit notice from being given as provided in Rule 4 of Colorado Rules
of Civil Procedure, as the same may be amended from time to time.

28. RULES AND REGULATIONS. It is further agreed that the rules and regulations
set forth on Exhibit D attached hereto shall be and are hereby made a part of
this Lease and Tenant agrees that Tenant's employees and agents or any others
permitted by Tenant to occupy or enter the Premises will at all times abide by
said rules and regulations. A breach of any of such rules or regulations shall
be deemed an Event of Default under this Lease and Landlord shall have all
remedies as set forth in Paragraph 19 hereof.

29. PARKING. Landlord agrees to make available to Tenant one (1) in and out
non-assigned parking space per one thousand (1,000) rentable square feet of the
Premises in the parking facilities (parking lot or parking structure) located on
block 159 or 1801 California block, made available by Landlord for use by
tenants in the Building, in Denver, Colorado, at the current rate charged for
such spaces from time to time (which rate is currently $130.00 per month per
non-assigned space, $160.00 to $185.00 per month per reserved space and $120.00
per month per space for the adjacent surface lot), and Tenant shall pay the
going monthly building rate for all such spaces it elects to lease. Tenant shall
notify Landlord in writing prior to the commencement date of the Primary Lease
Term of Tenant's acceptance of all or any portion of the spaces so offered, and
Landlord agrees to make the same available to Tenant within thirty (30) days
following the commencement date of the Primary Lease Term. The number of parking
spaces which Tenant elects to lease pursuant to the terms of this Paragraph
shall be evidenced on the Commencement Certificate attached hereto as Exhibit C
to be signed by Landlord and Tenant. In the event Tenant does not elect prior to
the Primary Lease Term to lease all parking spaces to which Tenant is entitled,
Tenant may thereafter at any time during the Lease Term elect to lease such
spaces on the terms set forth above upon 45 days' prior written notice to
Landlord. Tenant shall receive one bill monthly for all spaces

                                       24
<PAGE>   28

leased by it hereunder and Tenant shall pay for all spaces in one lump payment
directly to Landlord. The right granted to Tenant herein to use said parking
spaces shall be deemed a license only and Landlord's in ability to make such
spaces available at any time during the term of the Lease for reasons beyond
Landlord's reasonable control shall not be deemed a material breach by Landlord
of any of its obligations under the Lease. The abatement of Tenant's obligation
to pay for such spaces during any period the same are unavailable shall
constitute Tenant's sole remedy in the event of such unavailability. If at any
time during the term hereof Tenant fails to timely make payment of parking
rental due hereunder, Tenant shall forfeit its rights to all parking spaces
granted hereunder. Tenant may license additional parking spaces on a
month-to-month, as-available basis ("Month-to-Month Spaces"). Tenant
acknowledges that Landlord has the right to terminate Tenant's use of all or
any of such Month-to-Month Spaces upon 10 days' notice to Tenant.

30. SUBSTITUTE PREMISES. [INTENTIONALLY DELETED]

31. BROKERAGE. Tenant hereby represents and warrants that Tenant has not
employed any broker in regard to this Lease and that Tenant has no knowledge of
any broker being instrumental in bringing about this Lease transaction except
Cushman & Wakefield of Colorado, Inc., a Colorado corporation ("Cushman"), which
has acted as Landlord's leasing agent and CB Richard Ellis Inc. Tenant shall
indemnify Landlord against any expense incurred by Landlord as a result of any
claim for brokerage or other commissions made by any other broker, finder, or
agent, whether or not meritorious, employed by Tenant or claiming by, through,
or under Tenant. Tenant acknowledges that Landlord shall not be liable for any
representations by Cushman or CB Ricard Ellis Inc. regarding the Premises,
Building, or this lease transaction.

32. ERISA. Tenant represents as follows:

         A. Neither Tenant nor any of its affiliates (within the meaning of Part
V(c) of Prohibited Transaction Exemption 84-14, 49 Fed.Reg. 9494 (1984), as
amended ("PTE 84-14")) has, or during the immediately preceding year has,
exercised authority to:

               (1) appoint or terminate the Prudential Insurance Company of
America or Prudential Real Estate Investors ("Prudential") as investment
manager over assets of any employee benefit plan invested in Landlord; or

               (2) negotiate the terms of a management agreement with Prudential
on behalf of any such plan;

         B. Tenant is not a "related party" of Prudential (as defined in Part
V(h) of PTE 84-14);

         C. Tenant has negotiated and determined the terms of this Lease at
arm's length, as such terms would be negotiated and determined by Tenant
with unrelated parties; and

         D. Tenant is not an "employee benefit plan" as defined in Section 3(3)
of the Employee Retirement Income Security Act of 1974, as amended ("ERISA"), a
"plan" as defined in Section 4965 (e)(1) of the Internal Revenue Code of 1986,
as amended (the "Code") or any entity deemed to hold "plan assets" within the
meaning of 29 C.P.R. Section 2510.3-101 of any such employee benefit plan or
plan.

                                       25
<PAGE>   29

33, TIME OF ESSENCE. Time is of the essence herein.

         IN WITNESS WHEREOF, the parties hereto have caused this Lease to be
executed on the dates below their respective signatures. This Lease shall be
deemed effective upon delivery of a fully executed copy hereof to Tenant by
Landlord. Landlord and Tenant, by execution hereof, agree that the day and year
first above written shall be used for reference purposes only and shall not be
deemed the effective date hereof.

EXACTIS.COM, INC., a Delaware               THE PRUDENTIAL INSURANCE COMPANY OF
corporation                                 AMERICA, a New Jersey corporation

                                            By Cushman & Wakefield of Colorado,
By:   /s/ E. Thomas Detmer Jr.              Inc., a Colorado corporation,
  ----------------------------              Authorized Agent
Title:  President & CEO
      ------------------------
Date:        1/19/00
     ------------------------
            "Tenant"

                                            By: /s/ Illegible
                                               --------------------------------
                                                Director
                                            Date:        1/19/00
                                                -------------------------------
                                                        "Landlord"

                                       26<PAGE>   1

                                                                  Exhibit 10.16

               [GENERAL MOTORS ACCEPTANCE CORPORATION LETTERHEAD]

                                February 1, 1999

Mr. W. Marvin Rush
Rush Enterprises, Inc.
Rush Truck Group (RUSH)

SUBJECT: SPECIAL WHOLESALE INCENTIVE PLAN INTEREST RATE ALLOWANCES

From time to time GMAC offers to dealers a reduced interest rate on new and used
floor plan finance obligations. This special rate is offered for competitive
reasons as an incentive to encourage dealers to provide GMAC with . It is known
as the Wholesale Incentive Plan ("WIP").

This letter confirms GMAC's agreement to provide RUSH with the following WIP:

         New and used wholesale floor plan and Borrowing Base Line of Credit,
         will be net billed at Prime minus .50 p.p. with maximum Credit Account
         Plan (CAP) at 50% of wholesale floor plan outstandings (the amount
         earned in the CAP shall be at a rate equivalent to the amount payable
         to GMAC on wholesale floor plan, less .25 p.p.). To qualify for this
         reduction, minimum wholesale outstandings must total at least $25
         million, GMAC must retain all current wholesale outstandings for
         franchises presently owned and in the future and GMAC must be provided
         first right of refusal on all future wholesale financing.

The WIP becomes effective as of February 1, 1999. It will remain in effect
indefinitely, subject to modifications, restrictions, qualifications, or
outright cancellation by GMAC at any time in its sole and absolute discretion;
provided that absent any default by you, any such change in the WIP will not be
effective except upon a thirty (30) day notice to you.

Notwithstanding the foregoing, your wholesale credit lines are expressly subject
to the written terms of the Wholesale Security Agreement under which they were
extended. They are discretionary lines of credit and may be modified, suspended
or terminated at our election, and at our sole and absolute discretion.

                                                       W. G. Hartnuss
                                                       Area Manager

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