<PAGE>   1



                               CRITICAL PATH, INC.

                             1999 STOCK OPTION PLAN



        1. Purposes of the Plan. The purposes of this Nonstatutory Stock Option
Plan are:

        - to attract and retain the best available personnel for positions of
          substantial responsibility,

        - to provide additional incentive to Employees, Directors and
          Consultants, and

        - to promote the success of the Company's business.

        Options granted under the Plan will be Nonstatutory Stock Options.

        2. Definitions. As used herein, the following definitions shall apply:

                (a) "Administrator" means the Board or any of its Committees as
shall be administering the Plan, in accordance with Section 4 of the Plan.

                (b) "Applicable Laws" means the requirements relating to the
administration of stock option plans under U.S. state corporate laws, U.S.
federal and state securities laws, the Code, any stock exchange or quotation
system on which the Common Stock is listed or quoted and the applicable laws of
any foreign country or jurisdiction where Options are, or will be, granted under
the Plan.

                (c) "Board" means the Board of Directors of the Company.

                (d) "Code" means the Internal Revenue Code of 1986, as amended.

                (e) "Committee" means a committee of Directors appointed by the
Board in accordance with Section 4 of the Plan.

                (f) "Common Stock" means the Common Stock of the Company.

                (g) "Company" means Critical Path, Inc., a California
corporation.

                (h) "Consultant" means any person, including an advisor, engaged
by the Company or a Parent or Subsidiary to render services to such entity.

                (i) "Director" means a member of the Board.


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                (j) "Disability" means total and permanent disability as defined
in Section 22(e)(3) of the Code.

                (k) "Employee" means any person, including Officers, employed by
the Company or any Parent or Subsidiary of the Company. A Service Provider shall
not cease to be an Employee in the case of (i) any leave of absence approved by
the Company or (ii) transfers between locations of the Company or between the
Company, its Parent, any Subsidiary, or any successor. Neither service as a
Director nor payment of a director's fee by the Company shall be sufficient to
constitute "employment" by the Company.

                (l) "Exchange Act" means the Securities Exchange Act of 1934, as
amended.

                (m) "Fair Market Value" means, as of any date, the value of
Common Stock determined as follows:

                        (i) If the Common Stock is listed on any established
stock exchange or a national market system, including without limitation the
Nasdaq National Market or The Nasdaq SmallCap Market of The Nasdaq Stock Market,
its Fair Market Value shall be the closing sales price for such stock (or the
closing bid, if no sales were reported) as quoted on such exchange or system for
the last market trading day prior to the time of determination, as reported in
The Wall Street Journal or such other source as the Administrator deems
reliable;

                        (ii) If the Common Stock is regularly quoted by a
recognized securities dealer but selling prices are not reported, the Fair
Market Value of a Share of Common Stock shall be the mean between the high bid
and low asked prices for the Common Stock on the last market trading day prior
to the day of determination, as reported in The Wall Street Journal or such
other source as the Administrator deems reliable;

                        (iii) In the absence of an established market for the
Common Stock, the Fair Market Value shall be determined in good faith by the
Administrator.

                (n) "Notice of Grant" means a written or electronic notice
evidencing certain terms and conditions of an individual Option grant. The
Notice of Grant is part of the Option Agreement.

                (o) "Officer" means a person who is an officer of the Company
within the meaning of Section 16 of the Exchange Act and the rules and
regulations promulgated thereunder.

                (p) "Option" means a nonstatutory stock option granted pursuant
to the Plan, that is not intended to qualify as an incentive stock option within
the meaning of Section 422 of the Code and the regulations promulgated
thereunder.

                (q) "Option Agreement" means an agreement between the Company
and an Optionee evidencing the terms and conditions of an individual Option
grant. The Option Agreement is subject to the terms and conditions of the Plan.


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                (r) "Option Exchange Program" means a program whereby
outstanding options are surrendered in exchange for options with a lower
exercise price.

                (s) "Optioned Stock" means the Common Stock subject to an
Option.

                (t) "Optionee" means the holder of an outstanding Option granted
under the Plan.

                (u) "Parent" means a "parent corporation," whether now or
hereafter existing, as defined in Section 424(e) of the Code.

                (v) "Plan" means this 1999 Stock Option Plan.

                (w) "Service Provider" means an Employee including an Officer,
Consultant or Director.

                (x) "Share" means a share of the Common Stock, as adjusted in
accordance with Section 12 of the Plan.

                (y) "Subsidiary" means a "subsidiary corporation," whether now
or hereafter existing, as defined in Section 424(f) of the Code.

        3. Stock Subject to the Plan. Subject to the provisions of Section 12 of
the Plan, the maximum aggregate number of Shares which may be optioned and sold
under the Plan is 4,000,000 Shares. The Shares may be authorized, but unissued,
or reacquired Common Stock.

        If an Option expires or becomes unexercisable without having been
exercised in full, or is surrendered pursuant to an Option Exchange Program, the
unpurchased Shares which were subject thereto shall become available for future
grant or sale under the Plan (unless the Plan has terminated).

        4. Administration of the Plan.

                (a) Administration. The Plan shall be administered by (i) the
Board or (ii) a Committee, which committee shall be constituted to satisfy
Applicable Laws.

                (b) Powers of the Administrator. Subject to the provisions of
the Plan, and in the case of a Committee, subject to the specific duties
delegated by the Board to such Committee, the Administrator shall have the
authority, in its discretion:

                        (i) to determine the Fair Market Value of the Common
Stock;

                        (ii) to select the Service Providers to whom Options may
be granted hereunder;

                        (iii) to determine whether and to what extent Options
are granted hereunder;


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                        (iv) to determine the number of shares of Common Stock
to be covered by each Option granted hereunder;

                        (v) to approve forms of agreement for use under the
Plan;

                        (vi) to determine the terms and conditions, not
inconsistent with the terms of the Plan, of any award granted hereunder. Such
terms and conditions include, but are not limited to, the exercise price, the
time or times when Options may be exercised (which may be based on performance
criteria), any vesting acceleration or waiver of forfeiture restrictions, and
any restriction or limitation regarding any Option or the shares of Common Stock
relating thereto, based in each case on such factors as the Administrator, in
its sole discretion, shall determine;

                        (vii) to reduce the exercise price of any Option to the
then current Fair Market Value if the Fair Market Value of the Common Stock
covered by such Option shall have declined since the date the Option was
granted;

                        (viii) to institute an Option Exchange Program;

                        (ix) to construe and interpret the terms of the Plan and
awards granted pursuant to the Plan;

                        (x) to prescribe, amend and rescind rules and
regulations relating to the Plan, including rules and regulations relating to
sub-plans established for the purpose of qualifying for preferred tax treatment
under foreign tax laws;

                        (xi) to modify or amend each Option (subject to Section
14(b) of the Plan), including the discretionary authority to extend the
post-termination exercisability period of Options longer than is otherwise
provided for in the Plan;

                        (xii) to authorize any person to execute on behalf of
the Company any instrument required to effect the grant of an Option previously
granted by the Administrator;

                        (xiii) to determine the terms and restrictions
applicable to Options; and

                        (xiv) to make all other determinations deemed necessary
or advisable for administering the Plan.

                (c) Effect of Administrator's Decision. The Administrator's
decisions, determinations and interpretations shall be final and binding on all
Optionees and any other holders of Options.

        5. Eligibility. Options may be granted to Service Providers except
Officers and Directors; provided, however, that Options may be granted to
Officers in connection with the Officer's initial employment by the Company.

        6. Limitation. Neither the Plan nor any Option shall confer upon an
Optionee any right with respect to continuing the Optionee's relationship as a
Service Provider with the Company, nor


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<PAGE>   5

shall they interfere in any way with the Optionee's right or the Company's right
to terminate such relationship at any time, with or without cause.

        7. Term of Plan. The Plan shall become effective upon its adoption by
the Board. It shall continue in effect for ten (10) years, unless sooner
terminated under Section 14 of the Plan.

        8. Term of Option. The term of each Option shall be stated in the Option
Agreement.

        9. Option Exercise Price and Consideration.

                (a) Exercise Price. The per share exercise price for the Shares
to be issued pursuant to exercise of an Option shall be determined by the
Administrator.

                (b) Waiting Period and Exercise Dates. At the time an Option is
granted, the Administrator shall fix the period within which the Option may be
exercised and shall determine any conditions which must be satisfied before the
Option may be exercised.

                (c) Form of Consideration. The Administrator shall determine the
acceptable form of consideration for exercising an Option, including the method
of payment. Such consideration may consist entirely of:

                        (i) cash;

                        (ii) check;

                        (iii) promissory note;

                        (iv) other Shares which (A) in the case of Shares
acquired upon exercise of an option, have been owned by the Optionee for more
than six months on the date of surrender, and (B) have a Fair Market Value on
the date of surrender equal to the aggregate exercise price of the Shares as to
which said Option shall be exercised;

                        (v) consideration received by the Company under a
cashless exercise program implemented by the Company in connection with the
Plan;

                        (vi) a reduction in the amount of any Company liability
to the Optionee, including any liability attributable to the Optionee's
participation in any Company-sponsored deferred compensation program or
arrangement;

                        (vii) such other consideration and method of payment for
the issuance of Shares to the extent permitted by Applicable Laws; or

                        (viii) any combination of the foregoing methods of
payment.

        10. Exercise of Option.


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                (a) Procedure for Exercise; Rights as a Shareholder. Any Option
granted hereunder shall be exercisable according to the terms of the Plan and at
such times and under such conditions as determined by the Administrator and set
forth in the Option Agreement. An Option may not be exercised for a fraction of
a Share.

                An Option shall be deemed exercised when the Company receives:
(i) written or electronic notice of exercise (in accordance with the Option
Agreement) from the person entitled to exercise the Option, and (ii) full
payment for the Shares with respect to which the Option is exercised. Full
payment may consist of any consideration and method of payment authorized by the
Administrator and permitted by the Option Agreement and the Plan. Shares issued
upon exercise of an Option shall be issued in the name of the Optionee or, if
requested by the Optionee, in the name of the Optionee and his or her spouse.
Until the Shares are issued (as evidenced by the appropriate entry on the books
of the Company or of a duly authorized transfer agent of the Company), no right
to vote or receive dividends or any other rights as a shareholder shall exist
with respect to the Optioned Stock, notwithstanding the exercise of the Option.
The Company shall issue (or cause to be issued) such Shares promptly after the
Option is exercised. No adjustment will be made for a dividend or other right
for which the record date is prior to the date the Shares are issued, except as
provided in Section 12 of the Plan.

                Exercising an Option in any manner shall decrease the number of
Shares thereafter available, both for purposes of the Plan and for sale under
the Option, by the number of Shares as to which the Option is exercised.

                (b) Termination of Relationship as a Service Provider. If an
Optionee ceases to be a Service Provider, other than upon the Optionee's death
or Disability, the Optionee may exercise his or her Option, but only within such
period of time as is specified in the Option Agreement, and only to the extent
that the Option is vested on the date of termination (but in no event later than
the expiration of the term of such Option as set forth in the Option Agreement).
In the absence of a specified time in the Option Agreement, the Option shall
remain exercisable for three (3) months following the Optionee's termination.
If, on the date of termination, the Optionee is not vested as to his or her
entire Option, the Shares covered by the unvested portion of the Option shall
revert to the Plan. If, after termination, the Optionee does not exercise his or
her Option within the time specified by the Administrator, the Option shall
terminate, and the Shares covered by such Option shall revert to the Plan.

                (c) Disability of Optionee. If an Optionee ceases to be a
Service Provider as a result of the Optionee's Disability, the Optionee may
exercise his or her Option within such period of time as is specified in the
Option Agreement, to the extent the Option is vested on the date of termination
(but in no event later than the expiration of the term of such Option as set
forth in the Option Agreement). In the absence of a specified time in the Option
Agreement, the Option shall remain exercisable for twelve (12) months following
the Optionee's termination. If, on the date of termination, the Optionee is not
vested as to his or her entire Option, the Shares covered by the unvested
portion of the Option shall revert to the Plan. If, after termination, the
Optionee does not exercise his or her Option within the time specified herein,
the Option shall terminate, and the Shares covered by such Option shall revert
to the Plan.


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<PAGE>   7

                (d) Death of Optionee. If an Optionee dies while a Service
Provider, the Option may be exercised within such period of time as is specified
in the Option Agreement (but in no event later than the expiration of the term
of such Option as set forth in the Notice of Grant), by the Optionee's estate or
by a person who acquires the right to exercise the Option by bequest or
inheritance, but only to the extent that the Option is vested on the date of
death. In the absence of a specified time in the Option Agreement, the Option
shall remain exercisable for twelve (12) months following the Optionee's
termination. If, at the time of death, the Optionee is not vested as to his or
her entire Option, the Shares covered by the unvested portion of the Option
shall immediately revert to the Plan. The Option may be exercised by the
executor or administrator of the Optionee's estate or, if none, by the person(s)
entitled to exercise the Option under the Optionee's will or the laws of descent
or distribution. If the Option is not so exercised within the time specified
herein, the Option shall terminate, and the Shares covered by such Option shall
revert to the Plan.

                (e) Buyout Provisions. The Administrator may at any time offer
to buy out for a payment in cash or Shares, an Option previously granted based
on such terms and conditions as the Administrator shall establish and
communicate to the Optionee at the time that such offer is made.

        11. Non-Transferability of Options. Unless determined otherwise by the
Administrator, an Option may not be sold, pledged, assigned, hypothecated,
transferred, or disposed of in any manner other than by will or by the laws of
descent or distribution and may be exercised, during the lifetime of the
Optionee, only by the Optionee. If the Administrator makes an Option
transferable, such Option shall contain such additional terms and conditions as
the Administrator deems appropriate.

        12. Adjustments Upon Changes in Capitalization, Dissolution, Merger or
Asset Sale.

                (a) Changes in Capitalization. Subject to any required action by
the shareholders of the Company, the number of shares of Common Stock covered by
each outstanding Option, and the number of shares of Common Stock which have
been authorized for issuance under the Plan but as to which no Options have yet
been granted or which have been returned to the Plan upon cancellation or
expiration of an Option, as well as the price per share of Common Stock covered
by each such outstanding Option, shall be proportionately adjusted for any
increase or decrease in the number of issued shares of Common Stock resulting
from a stock split, reverse stock split, stock dividend, combination or
reclassification of the Common Stock, or any other increase or decrease in the
number of issued shares of Common Stock effected without receipt of
consideration by the Company; provided, however, that conversion of any
convertible securities of the Company shall not be deemed to have been "effected
without receipt of consideration." Such adjustment shall be made by the Board,
whose determination in that respect shall be final, binding and conclusive.
Except as expressly provided herein, no issuance by the Company of shares of
stock of any class, or securities convertible into shares of stock of any class,
shall affect, and no adjustment by reason thereof shall be made with respect to,
the number or price of shares of Common Stock subject to an Option.

                (b) Dissolution or Liquidation. In the event of the proposed
dissolution or liquidation of the Company, the Administrator shall notify each
Optionee as soon as practicable prior to the effective date of such proposed
transaction. The Administrator in its discretion may provide


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<PAGE>   8

for an Optionee to have the right to exercise his or her Option until ten (10)
days prior to such transaction as to all of the Optioned Stock covered thereby,
including Shares as to which the Option would not otherwise be exercisable. In
addition, the Administrator may provide that any Company repurchase option
applicable to any Shares purchased upon exercise of an Option shall lapse as to
all such Shares, provided the proposed dissolution or liquidation takes place at
the time and in the manner contemplated. To the extent it has not been
previously exercised, an Option will terminate immediately prior to the
consummation of such proposed action.

                (c) Merger or Asset Sale. In the event of a merger of the
Company with or into another corporation, or the sale of substantially all of
the assets of the Company, each outstanding Option shall be assumed or an
equivalent option or right substituted by the successor corporation or a Parent
or Subsidiary of the successor corporation. In the event that the successor
corporation refuses to assume or substitute for the Option, the Optionee shall
fully vest in and have the right to exercise the Option as to all of the
Optioned Stock, including Shares as to which it would not otherwise be vested or
exercisable. If an Option becomes fully vested and exercisable in lieu of
assumption or substitution in the event of a merger or sale of assets, the
Administrator shall notify the Optionee in writing or electronically that the
Option shall be fully vested and exercisable for a period of fifteen (15) days
from the date of such notice, and the Option shall terminate upon the expiration
of such period. For the purposes of this paragraph, the Option shall be
considered assumed if, following the merger or sale of assets, the option or
right confers the right to purchase or receive, for each Share of Optioned
Stock, immediately prior to the merger or sale of assets, the consideration
(whether stock, cash, or other securities or property) received in the merger or
sale of assets by holders of Common Stock for each Share held on the effective
date of the transaction (and if holders were offered a choice of consideration,
the type of consideration chosen by the holders of a majority of the outstanding
Shares); provided, however, that if such consideration received in the merger or
sale of assets is not solely common stock of the successor corporation or its
Parent, the Administrator may, with the consent of the successor corporation,
provide for the consideration to be received upon the exercise of the Option,
for each Share of Optioned Stock to be solely common stock of the successor
corporation or its Parent equal in fair market value to the per share
consideration received by holders of Common Stock in the merger or sale of
assets.

        13. Date of Grant. The date of grant of an Option shall be, for all
purposes, the date on which the Administrator makes the determination granting
such Option, or such other later date as is determined by the Administrator.
Notice of the determination shall be provided to each Optionee within a
reasonable time after the date of such grant.

        14. Amendment and Termination of the Plan.

                (a) Amendment and Termination. The Board may at any time amend,
alter, suspend or terminate the Plan.

                (b) Effect of Amendment or Termination. No amendment,
alteration, suspension or termination of the Plan shall impair the rights of any
Optionee, unless mutually agreed otherwise between the Optionee and the
Administrator, which agreement must be in writing and signed by the Optionee and
the Company. Termination of the Plan shall not affect the Administrator's
ability to


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<PAGE>   9

exercise the powers granted to it hereunder with respect to options granted
under the Plan prior to the date of such termination.

        15. Conditions Upon Issuance of Shares.

                (a) Legal Compliance. Shares shall not be issued pursuant to the
exercise of an Option unless the exercise of such Option and the issuance and
delivery of such Shares shall comply with Applicable Laws and shall be further
subject to the approval of counsel for the Company with respect to such
compliance.

                (b) Investment Representations. As a condition to the exercise
of an Option the Company may require the person exercising such Option to
represent and warrant at the time of any such exercise that the Shares are being
purchased only for investment and without any present intention to sell or
distribute such Shares if, in the opinion of counsel for the Company, such a
representation is required.

        16. Inability to Obtain Authority. The inability of the Company to
obtain authority from any regulatory body having jurisdiction, which authority
is deemed by the Company's counsel to be necessary to the lawful issuance and
sale of any Shares hereunder, shall relieve the Company of any liability in
respect of the failure to issue or sell such Shares as to which such requisite
authority shall not have been obtained.

        17. Reservation of Shares. The Company, during the term of this Plan,
will at all times reserve and keep available such number of Shares as shall be
sufficient to satisfy the requirements of the Plan.


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                               CRITICAL PATH, INC.

                             1999 STOCK OPTION PLAN

                             STOCK OPTION AGREEMENT

        Unless otherwise defined herein, the terms defined in the Plan shall
have the same defined meanings in this Option Agreement.

I. NOTICE OF STOCK OPTION GRANT

        [OPTIONEE'S NAME AND ADDRESS]

        You have been granted an option to purchase Common Stock of the Company,
subject to the terms and conditions of the Plan and this Option Agreement, as
follows:

        Grant Number
                                             --------------------------

        Date of Grant
                                             --------------------------

        Vesting Commencement Date
                                             --------------------------

        Exercise Price per Share            $
                                             --------------------------

        Total Number of Shares Granted
                                             --------------------------

        Total Exercise Price                $
                                             --------------------------

        Type of Option:                      Nonstatutory Stock Option
                                             --------------------------

        Term/Expiration Date:
                                             --------------------------

        Vesting Schedule:
                                             --------------------------

        Subject to the Optionee continuing to be a Service Provider on such
dates, this Option shall vest and become exercisable in accordance with the
following schedule:

        [25% OF THE SHARES SUBJECT TO THE OPTION SHALL VEST TWELVE MONTHS AFTER
THE VESTING COMMENCEMENT DATE, AND 1/48TH OF THE SHARES SUBJECT TO THE OPTION
SHALL VEST UPON THE LAST DAY OF EACH MONTH THEREAFTER.]


<PAGE>   11


        Termination Period:

        This Option may be exercised for 30 days after Optionee ceases to be a
Service Provider. Upon the death or Disability of the Optionee, this Option may
be exercised for 6 months following the date of death or Disability of the
Optionee. In no event shall this Option be exercised later than the
Term/Expiration Date as provided above.

II. AGREEMENT

        1. Grant of Option. The Plan Administrator of the Company hereby grants
to the Optionee named in the Notice of Grant attached as Part I of this
Agreement (the "Optionee") an option (the "Option") to purchase the number of
Shares, as set forth in the Notice of Grant, at the exercise price per share set
forth in the Notice of Grant (the "Exercise Price"), subject to the terms and
conditions of the Plan, which is incorporated herein by reference. In the event
of a conflict between the terms and conditions of the Plan and the terms and
conditions of this Option Agreement, the terms and conditions of the Plan shall
prevail.

        2. Exercise of Option.

                (a) Right to Exercise. This Option is exercisable during its
term in accordance with the Vesting Schedule set out in the Notice of Grant and
the applicable provisions of the Plan and this Option Agreement.

                (b) Method of Exercise. This Option is exercisable by delivery
of an exercise notice, in the form attached as Exhibit A (the "Exercise
Notice"), which shall state the election to exercise the Option, the number of
Shares in respect of which the Option is being exercised (the "Exercised
Shares"), and such other representations and agreements as may be required by
the Company pursuant to the provisions of the Plan. The Exercise Notice shall be
completed by the Optionee and delivered to the Manager of Stock Compliance and
Equity Compensation. The Exercise Notice shall be accompanied by payment of the
aggregate Exercise Price as to all Exercised Shares. This Option shall be deemed
to be exercised upon receipt by the Company of such fully executed Exercise
Notice accompanied by such aggregate Exercise Price.

                No Shares shall be issued pursuant to the exercise of this
Option unless such issuance and exercise complies with Applicable Laws. Assuming
such compliance, for income tax purposes the Exercised Shares shall be
considered transferred to the Optionee on the date the Option is exercised with
respect to such Exercised Shares.

        3. Lock-Up Period. Optionee hereby agrees that, if so requested by the
Company or any representative of the underwriters (the "Managing Underwriter")
in connection with any registration of the offering of any securities of the
Company under the Securities Act, Optionee shall not sell or otherwise transfer
any Shares or other securities of the Company during the 180-day period (or such
other period as may be requested in writing by the Managing Underwriter and
agreed to in writing by the Company) (the "Market Standoff Period") following
the effective date of the Company's initial public offering. The Company may
impose stop-transfer instructions with respect to securities subject to the
foregoing restrictions until the end of such Market Standoff Period.


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<PAGE>   12

        4. Method of Payment. Payment of the aggregate Exercise Price shall be
by any of the following, or a combination thereof, at the election of the
Optionee:

                (a) cash;

                (b) check;

                (c) consideration received by the Company under a cashless
exercise program implemented by the Company in connection with the Plan; or

                (d) surrender of other Shares which (i) in the case of Shares
acquired upon exercise of an option, have been owned by the Optionee for more
than six (6) months on the date of surrender, AND (ii) have a Fair Market Value
on the date of surrender equal to the aggregate Exercise Price of the Exercised
Shares.

        5. Non-Transferability of Option. This Option may not be transferred in
any manner otherwise than by will or by the laws of descent or distribution and
may be exercised during the lifetime of Optionee only by the Optionee. The terms
of the Plan and this Option Agreement shall be binding upon the executors,
administrators, heirs, successors and assigns of the Optionee.

        6. Term of Option. This Option may be exercised only within the term set
out in the Notice of Grant, and may be exercised during such term only in
accordance with the Plan and the terms of this Option Agreement.

        7. Tax Consequences. Some of the federal tax consequences relating to
this Option, as of the date of this Option, are set forth below. THIS SUMMARY IS
NECESSARILY INCOMPLETE, AND THE TAX LAWS AND REGULATIONS ARE SUBJECT TO CHANGE.
THE OPTIONEE SHOULD CONSULT A TAX ADVISOR BEFORE EXERCISING THIS OPTION OR
DISPOSING OF THE SHARES.

                (a) Exercising the Option. The Optionee may incur regular
federal income tax liability upon exercise of an NSO. The Optionee will be
treated as having received compensation income (taxable at ordinary income tax
rates) equal to the excess, if any, of the Fair Market Value of the Exercised
Shares on the date of exercise over their aggregate Exercise Price. If the
Optionee is an Employee or a former Employee, the Company will be required to
withhold from his or her compensation or collect from Optionee and pay to the
applicable taxing authorities an amount in cash equal to a percentage of this
compensation income at the time of exercise, and may refuse to honor the
exercise and refuse to deliver Shares if such withholding amounts are not
delivered at the time of exercise.

                (b) Disposition of Shares. If the Optionee holds NSO Shares for
at least one year, any gain realized on disposition of the Shares will be
treated as long-term capital gain for federal income tax purposes.

        8. Entire Agreement; Governing Law. The Plan is incorporated herein by
reference. The Plan and this Option Agreement constitute the entire agreement of
the parties with respect to the subject matter hereof and supersede in their
entirety all prior undertakings and agreements of the


                                      -3-
<PAGE>   13

Company and Optionee with respect to the subject matter hereof, and may not be
modified adversely to the Optionee's interest except by means of a writing
signed by the Company and Optionee. This agreement is governed by the internal
substantive laws, but not the choice of law rules, of California.

        9. NO GUARANTEE OF CONTINUED SERVICE. OPTIONEE ACKNOWLEDGES AND AGREES
THAT THE VESTING OF SHARES PURSUANT TO THE VESTING SCHEDULE HEREOF IS EARNED
ONLY BY CONTINUING AS A SERVICE PROVIDER AT THE WILL OF THE COMPANY (AND NOT
THROUGH THE ACT OF BEING HIRED, BEING GRANTED AN OPTION OR PURCHASING SHARES
HEREUNDER). OPTIONEE FURTHER ACKNOWLEDGES AND AGREES THAT THIS AGREEMENT, THE
TRANSACTIONS CONTEMPLATED HEREUNDER AND THE VESTING SCHEDULE SET FORTH HEREIN DO
NOT CONSTITUTE AN EXPRESS OR IMPLIED PROMISE OF CONTINUED ENGAGEMENT AS A
SERVICE PROVIDER FOR THE VESTING PERIOD, FOR ANY PERIOD, OR AT ALL, AND SHALL
NOT INTERFERE WITH OPTIONEE'S RIGHT OR THE COMPANY'S RIGHT TO TERMINATE
OPTIONEE'S RELATIONSHIP AS A SERVICE PROVIDER AT ANY TIME, WITH OR WITHOUT
CAUSE.

        By your signature and the signature of the Company's representative
below, you and the Company agree that this Option is granted under and governed
by the terms and conditions of the Plan and this Option Agreement. Optionee has
reviewed the Plan and this Option Agreement in their entirety, has had an
opportunity to obtain the advice of counsel prior to executing this Option
Agreement and fully understands all provisions of the Plan and Option Agreement.
Optionee hereby agrees to accept as binding, conclusive and final all decisions
or interpretations of the Administrator upon any questions relating to the Plan
and Option Agreement. Optionee further agrees to notify the Company upon any
change in the residence address indicated below.


OPTIONEE                                    CRITICAL PATH, INC.


-----------------------------------         ------------------------------------
Signature                                   By


-----------------------------------         ------------------------------------
Print Name                                  Title


-----------------------------------
Residence Address


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                                    EXHIBIT A

                               CRITICAL PATH, INC.

                             1999 STOCK OPTION PLAN

                                 EXERCISE NOTICE



        Critical Path, Inc.
        320 First Street
        San Francisco, CA  94105





        Attention: Manager, Stock Compliance and Equity Compensation

        1. Exercise of Option. Effective as of today, ________________, _____,
the undersigned ("Purchaser") hereby elects to purchase ______________ shares
(the "Shares") of the Common Stock of Critical Path, Inc. (the "Company") under
and pursuant to the 1999 Nonstatutory Stock Option Plan (the "Plan") and the
Stock Option Agreement dated ______, ___ , Grant Number _______ (the "Option
Agreement"). The purchase price for the Shares shall be $_______, as required by
the Option Agreement.

        2. Delivery of Payment. Purchaser herewith delivers to the Company the
full purchase price for the Shares.

        3. Representations of Purchaser. Purchaser acknowledges that Purchaser
has received, read and understood the Plan and the Option Agreement and agrees
to abide by and be bound by their terms and conditions.

        4. Rights as Shareholder. Until the issuance (as evidenced by the
appropriate entry on the books of the Company or of a duly authorized transfer
agent of the Company) of the Shares, no right to vote or receive dividends or
any other rights as a shareholder shall exist with respect to the Optioned
Stock, notwithstanding the exercise of the Option. The Shares so acquired shall
be issued to the Optionee as soon as practicable after exercise of the Option.
No adjustment will be made for a dividend or other right for which the record
date is prior to the date of issuance, except as provided in Section 12 of the
Plan.

        5. Tax Consultation. Purchaser understands that Purchaser may suffer
adverse tax consequences as a result of Purchaser's purchase or disposition of
the Shares. Purchaser represents that Purchaser has consulted with any tax
consultants Purchaser deems advisable in connection with


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the purchase or disposition of the Shares and that Purchaser is not relying on
the Company for any tax advice.

        6. Entire Agreement; Governing Law. The Plan and Option Agreement are
incorporated herein by reference. This Agreement, the Plan and the Option
Agreement constitute the entire agreement of the parties with respect to the
subject matter hereof and supersede in their entirety all prior undertakings and
agreements of the Company and Purchaser with respect to the subject matter
hereof, and may not be modified adversely to the Purchaser's interest except by
means of a writing signed by the Company and Purchaser. This agreement is
governed by the internal substantive laws, but not the choice of law rules, of
California.

Submitted by:                               Accepted by:

PURCHASER                                   CRITICAL PATH, INC.


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Signature                                   By


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Print Name                                  Title


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                                            Date Received


Address:                                    Address:   320 First Street
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                                                       San Francisco, CA  94105

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