Document:

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                                                                    EXHIBIT 10.4

March 22, 2000

Mr. Thomas Davidsson
Runebergsgatan 4
114 29 Stockholm
Sweden

Dear Thomas:

On the behalf of Digex, Inc., I am pleased to offer you the position of Senior
Vice President for Europe at Digex, Inc., reporting to myself, Mark Shull, Chief
Executive Officer, Digex, Inc. You will be an employee of our wholly owned Digex
Sweden subsidiary, which is in the process of being established. This is a
regular full-time position and will be based in Sweden. You will be expected to
travel extensively.

We will look to you to lead the planning and execution of our expansion into
Europe and in mobile applications hosting globally. We anticipate that this will
result in your holding a Managing Director position in Digex Europe and becoming
the General Manager for our mobile applications hosting business globally.

We hope that you will be able to join us on the first of April 2000.

Base Salary
In this position, your annual base salary will be SEK 1,800,000. Base salary
will be payable in arrears in twelve installments per annum. Salaries are
reviewed annually on an anniversary basis, and increases are granted in
accordance with Company policy.

Incentive Compensation
You will be eligible to participate in Digex's Executive Management Incentive
Compensation Plan. In this position, you will be eligible for a bonus of 50% of
your base salary. At 100% of objectives achievement your total potential cash
compensation is SEK 2,700,000.

The incentive will be prorated on the base pay received during the current
fiscal calendar year. This incentive opportunity is contingent upon the
achievement of corporate and individual objectives as determined by your
management. This bonus is evaluated and paid on an annual basis.
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Mr. Thomas Davidsson
March 22, 2000
Page 2

Car
In this assignment, Digex will provide you with a vehicle in line with the
Company Car Policy. In your position, standard of car shall be equivalent to a
Saab 95 (Fuel expenses for business and private use and all maintenance costs
are included).

You can alternatively elect to receive a car allowance in cash, paid out per
month on a cost neutral basis.

Share Option Scheme
Digex is currently working on the design of a stock option plan for its European
employees. You will be eligible for inclusion in the share option scheme of
Digex Europe. All conditions related to the Share Option Scheme are set and
decisions made at the Company's absolute discretion. Any change of conditions
shall not constitute breach of this agreement.

As an alternative to your participation in the future Digex stock incentive plan
for European employees, Digex could extend you the opportunity to participate to
the US stock incentive plan under the condition that Digex would not incur any
employer's tax liability on your behalf.

Accordingly, you will arrange your personal location and circumstances to
mitigate or eliminate any charge to tax whatsoever on the employer/Digex that
might arise from, in connection with or by reference to your holding of any
stock options under the Digex Stock Incentive Plan or any dealing release or
exercise relating thereto.

On that basis, this offer would include a stock option grant covering an
aggregate of 200,000 shares of Digex common stock contingent upon approval by
the Compensation Committee of the Board of Directors. You will be granted
180,000 shares at an exercise price equal to the market price of Digex Inc.
common stock on the date that the grant is approved and the remaining 20,000
shares at an exercise price equal to $50.00 less than the strike price of the
first part of the grant.

Vesting of the award will begin with the approval of the grant and will continue
over a four-year period. 25% of the shares covered by the option will vest one
year following the date of grant. The balance of the shares will vest in equal
quarterly installments over the next three years so long as you continue to be
employed by Digex. Additionally, upon a change in control of the company, this
grant will fully vest one year following such change. Details will be provided
in your Grant Agreement upon approval by the Board of Directors. The option will
be issued pursuant to the Company's US long-term Incentive Plan and will be
subject to all the terms and conditions of that plan.

Benefits
As an employee of Digex you will be entitled to all employee benefits offered to
Digex's senior management in Europe.
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Mr. Thomas Davidsson
March 22, 2000
Page 3

Short Term Cash Sickness Benefit
In the event of the Employee being unable to discharge his duties, the Company
will pay the Employee a short-term cash sickness benefit in line with common
practice in Swedish Industry. After 90 days of continuous illness, the pension
insurance will come into force and pay a long-term disability pension.

Pension & Insurance Coverage
The Company will annually contribute towards a pension scheme selected and
designed by the Employee, "Ordinary Retirement Scheme". Company contribution
shall be equal to the maximum amount deductible (10 base amounts, currently SEK
366,000 per annum). Social charges on levied contributions to pension
arrangements will be paid by the Company. Disability coverage and survivor's
benefits shall be a part of the arrangement and be on a satisfactory level.
Retirement age is 65.

Holiday Entitlement
Vacation will be granted in accordance to Digex's European vacation policy for
senior management employees.

Termination of Agreement
The agreement may be terminated by either party giving to the other six months
advance notice in writing. The Company reserves the right to remove the Employee
from his position during the time of notice period. During the notice period the
Employee is entitled to the conditions of this agreement.

Should the agreement be terminated by the Company for any reason other than
material breach of agreement, the Employee shall receive in addition to time of
notice a severance pay amounting to six months salary as per date the day before
giving notice. The severance pay shall, unless otherwise agreed upon, be paid
every month starting the first month after the effective date of termination.

The Company reserves the right to terminate this agreement at any time without
advance notice or severance pay in the event of material breach of contract,
including act of gross negligence or gross misconduct by the Employee and
willful failure to perform his duties with the Company. Material breach of
contract after the termination of employment may result in the immediate
cessation of severance pay and other benefits.

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Mr. Thomas Davidsson
March 22, 2000
Page 4

Jurisdiction
This offer is construed according to the laws of the state of Delaware, USA
applicable to contracts made and to be performed in that state. Any dispute
about the agreement shall be submitted to an Arbitration court if the parties
cannot come to a consensus as to the interpretation of the conditions. Cost for
the arbitration proceedings shall be defrayed by the Company provided the
Employee has not unduly instigated the arbitration procedure. In such case, the
arbitrators shall determine the distribution of arbitration cost.

Other Employment Conditions
This offer is contingent on the following:

Your acknowledgement and execution of our "Employee Agreement Regarding
Intellectual Property and Proprietary Information", "Conflict of Interest and
Disclosure of Confidential Information" and which will be reviewed and
authorized by you and a company representative.

Kindly acknowledge your acceptance of this offer by signing and dating the
enclosed copy of this letter and returning it to me by the 27th of March 2000.
If we do not receive your acceptance of this offer by the close of business on
the above date, this offer will be withdrawn without further liability of either
party to the other.

If you have any questions or need additional information, please feel free to
call me at (240) 264-2470 or Tim Adams, Chief Financial Officer, 240 264-2635,
tadams@digex.com. I am looking forward to your joining the Digex Executive Team
and feel it will be a mutually beneficial relationship. I wish you success in
the continuation of your career with Digex.

Sincerely yours,

/s/  MARK SHULL

Mark Shull
President &
Chief Executive Officer
Digex, Inc.

cc:      D. Ruberg

Enclosure

                              /s/  THOMAS DAVIDSSON            March 22, 2000
                              ----------------------------     --------------
                              Accepted:   Thomas Davidsson     Date:<PAGE>

                                                                    EXHIBIT 10.5

July 5, 2000

Mr. Todd Carlson
1000 Blue Ridge Place
Richardson, TX   75080

Dear Todd:

On the behalf of Digex Incorporated, I am pleased to offer you the position of
Senior Vice President of Business Operations, reporting to Mark Shull, Chief
Executive Officer. This is a regular part time position that will require you to
work in the Washington, DC area a minimum of 10 days per month.

Compensation
Your annual base salary will be $125,000 (based on 52 weeks of service).
Salaries are reviewed annually, and increases are granted based on individual
performance during the year and in accordance with Company policy.

You will be eligible to participate in Digex's Executive Management Incentive
Compensation Plan. In this position, you will be eligible for a bonus of 50% of
your base salary. At 100% of objective achievement your total potential cash
compensation is $187,500.

The incentive will be prorated on the base pay received during the current
fiscal calendar year. This incentive opportunity is contingent upon the
achievement of corporate and individual objectives as determined by your
departmental management.

Stocks
This offer includes a stock option grant covering an aggregate of 125,000 shares
of Digex common stock contingent upon approval by the Compensation Committee of
the Board of Directors. You will be granted 100,000 shares at an exercised price
equal to the market price of Digex Inc. common stock on the date that the grant
is approved and the remaining 25,000 shares at an exercised price equal to
$20.00 less than the market price referenced above.

Vesting of the award will begin with the approval of the grant and will continue
over a four-year period. 25% of the shares covered by the option will vest one
year following the date of grant. The balance of the shares will vest in equal
quarterly installments over the next three years so long as you continue to be
employed by Digex. Additionally, upon a "change in control" as defined in the
stock option plan (attached), this grant will fully vest one year following such
change.

Details will be provided in your Grant Agreement upon approval by the Board of
Directors. The option will be issued pursuant to the Company's long-term
Incentive Plan and will be subject to all the terms and conditions of that plan.

Benefits
As an employee of Digex you will be entitled to all employee benefits: Medical
insurance, medical and prescription drug card, dental insurance, short and
long-term disability, life insurance, 401(k) plan, educational reimbursement,
holidays, sick leave, vacation time, military leave, bereavement leave, voting
time off and jury duty leave. Your medical benefits will be effective the first
day of the month following your start of employment. An outline of these
benefits is attached. Should you have any benefit questions, please contact Ms.
Marilyn Garner, Senior Human Resources Generalist, 240-264-2391.
<PAGE>

Todd Carlson
page 2
July 5, 2000

Temporary Housing/Commuting Expenses
This offer does not include relocation, however Digex will provide suitable
temporary housing and commuting expenses on an ongoing basis while employed at
Digex. It is understood that you will be located in Dallas, Texas. However you
are expected to work a minimum of ten (10) days per month in the Washington, DC
area.

This offer is contingent on the following:
 .    Your acknowledgement and execution of our "Employee Agreement Regarding
     Intellectual Property and Proprietary Information", which will be reviewed
     and authorized by you and a company representative.
 .    Proof that you are legally authorized to work in the United States per
     Immigration Reform Act of 1986 (see attachment A).
 .    Completion of the enclosed employment application.

As you know, in the ordinary course of business, pay and benefits plans evolve
as laws, employee, and / or business need change. If, in the future, it becomes
necessary to change any of the benefit or compensation plans currently in
effect, these changes will apply to you as they do to other eligible employees.
Furthermore, while this letter is our commitment to employ you in the previously
mentioned position, it does not constitute a contract for a specific length of
employment.

Kindly acknowledge your acceptance of this offer by signing and dating the
enclosed copy of this letter and returning it to me by July 14, 2000. If we do
not receive your acceptance of this offer by the close of business on the above
date, this offer will be withdrawn without further liability of either party to
the other.

If you have any questions or need additional information, please feel free to
call me at (240) 264-4712 or fax at (240) 264-2666. I am looking forward to your
joining the Digex Executive Management Team and feel it will be a mutually
beneficial relationship. I wish you success in the continuation of your career
with Digex.

Sincerely yours,

/s/ DAVID GAY

David Gay
Director of Employment

cc:      M. Shull
         D. Ruberg

Encl.

/s/ TODD CARLSON                   7/8/00           7/1/00
----------------------------     ----------       -------------
Accepted: Todd Carlson              Date:          Start Date:

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