Document:

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                                                                    EXHIBIT 10.2

                    1996 ISOCOR DIRECTORS' STOCK OPTION PLAN

                              AMENDED AND RESTATED

                               AS OF MAY 13, 1999

     1. Purposes of the Plan. The purposes of this Directors' Stock Option Plan
are to attract and retain the best available personnel for service as Directors
of the Company, to provide additional incentive to the Outside Directors of the
Company to serve as Directors, and to encourage their continued service on the
Board.

     All options granted hereunder shall be "nonstatutory" stock options".

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

          (a) "Board" shall mean the Board of Directors of the Company.

          (b) "Code" shall mean the Internal Revenue Code of 1986, as amended.

          (c) "Common Stock" shall mean the Common Stock of the Company.

          (d) "Company" shall mean ISOCOR, a California corporation.

          (e) "Continuous Status as a Director" shall mean the absence of any
interruption or termination of service as a Director.

          (f) "Director" shall mean a member of the Board.

          (g) "Employee" shall mean any person, including officers and
directors, employed by the Company or any Parent or Subsidiary of the Company.
The payment of a director's fee by the Company shall not be sufficient in and of
itself to constitute "employment" by the Company.

          (h) "Exchange Act" shall mean the Security Exchange Act of 1934, as
amended.

          (i) "Option" shall mean a stock option granted pursuant to the Plan.

          (j) "Optioned Stock" shall mean the Common Stock subject to an Option.

          (k) "Optionee" shall mean an Outside Director who receives an Option.

          (l) "Outside Director" shall mean a Director who is not an Employee.

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

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          (n) "Plan" shall mean this 1996 Directors' Stock Option Plan.

          (o) "Share" shall mean a share of the Common Stock, as adjusted in
accordance with Section 11 of the Plan.

          (p) "Subsidiary" shall mean 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 11 of
the Plan, the maximum aggregate number of Shares which may be optioned and sold
under the Plan is 150,000 Shares (the "Pool") of Common Stock. The Shares may be
authorized, but unissued, or reacquired Common Stock.

     If an Option should expire or become unexercisable for any reason without
having been exercised in full, the unpurchased Shares which were subject thereto
shall, unless the Plan shall have been terminated, become available for future
grant under the Plan- If Shares which were acquired upon exercise of an Option
are subsequently repurchased by the Company, such Shares shall not in any event
be returned to the Plan and shall not become available for future grant under
the Plan.

     4. Administration of and Grants of Options under the Plan.

          (a) Administrator. Except as otherwise required herein, the Plan shall
be administered by the Board.

          (b) Procedure for Grants. All grants of Options hereunder shall be
automatic and nondiscretionary and shall be made strictly in accordance with the
following provisions:

               (i) No person shall have any discretion to select which Outside
Directors shall be granted Options or to determine the number of Shares to be
covered by Options granted to Outside Directors.

               (ii) Each Outside Director who has not, prior to the Company's
initial offering of Common Stock to the public, received an option grant
pursuant to the Company's 1992 Stock. Option Plan, shall be automatically
granted an Option to purchase 25,000 Shares (the "First Option") on the date on
which the later of the following events occurs: (A) January 18, 1996, or (B) the
date on which such person first becomes an Outside Director, whether through
election by the shareholders of the Company or appointment by the Board of
Directors to fill a vacancy.

               (iii) Each Outside Director who has, prior to the Company's
initial offering of Common Stock to the public, received an option grant
pursuant to the Company's 1992 Stock Option Plan, shall be automatically granted
an Option to purchase 5,000 Shares (the "Modified First Option") on the date on
which the later of the following events occurs: (A) January 18, 1996, or (B) the
date on which such person first becomes an Outside Director, whether through
election by the shareholders of the Company or appointment by the Board of
Directors to fill a vacancy,

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               (iv) After the First Option has been granted to an Outside
Director, such Outside Director (including Directors who have received a
Modified First Option) shall thereafter be automatically granted an Option to
purchase 6,250 Shares (a "Subsequent Option") on the first calendar day of the
Company's fiscal year, provided that, on such date, he or she shall have served
on the Board for at least six (6) months.

               (v) Notwithstanding the provisions of subsections (ii) and (iii)
hereof, in the event that a grant would cause the number of Shares subject to
outstanding Options plus the number of Shares previously purchased upon exercise
of Options to exceed the Pool, then each such automatic grant shall be for that
number of Shares determined by dividing the total number of Shares remaining
available for grant by the number of Outside Directors on the automatic grant
date. Any further grants shall then be deferred until such time, if any, as
additional Shares become available for grant under the Plan through action of
the shareholders to increase the number of Shares which may be issued under the
Plan or through cancellation or expiration of Options previously granted
hereunder.

               (vi) Notwithstanding the provisions of subsections (ii) and (iii)
hereof any grant of an Option made before the Company has obtained shareholder
approval of the Plan in accordance with Section 17 hereof shall be conditioned
upon obtaining such shareholder approval of the Plan in accordance with Section
17 hereof.

               (vii) The terms of each First Option granted hereunder shall be
as follows:

                    (1) the First Option shall be exercisable only while the
Outside Director remains a Director of the Company, except as set forth in
Section 9 hereof.

                    (2) the exercise price per Share shall be 100% of the fair
market value per Share at le beginning of the date of grant of the First Option,
determined in accordance with Section 8 hereof

                    (3) the First Option shall become exercisable in
installments cumulatively as to 25% of the Shares subject to the First Option on
each of the first, second, third and fourth anniversaries of the date of grant
of the First Option.

               (viii) The terms of each Modified First Option granted hereunder
shall be as follows;

                    (1) the Modified First Option on shall be exercisable only
while the Outside Director remains a Director of the Company, except as set
forth in Section 9 hereof.

                    (2) the exercise price per Share shall be 100% of the fair
market value per Share at the beginning of the date of grant of the First
Option, determined in accordance with Section 8 hereof.

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                    (3) the Modified First Option shall become exercisable in
installments cumulatively as to 50% of the Shares subject to the Modified First
Option on each of the third and fourth anniversaries of the due of grant of the
Modified First Option.

               (ix) The terms of each Subsequent Option granted hereunder shall
be as follows:

                    (1) the Subsequent Option shall be exercisable only while
the Outside Director remains a Director of the Company, except as set forth in
Section 9 hereof.

                    (2) the exercise price per Share shall be 100% of the fair
market value per Share at the beginning of the date of grant of the Subsequent
Option, determined in accordance with Section 8 hereof.

                    (3) the Subsequent Option shall become exercisable as to one
hundred percent (100%) of the Shares subject to the Subsequent Option on the
fourth anniversary of the date of grant of the Subsequent Option.

          (c) Powers of the Board. Subject to the provisions and restrictions of
the Plan, the Board shall have the authority, in its discretion: (i) to
determine, upon review of relevant information and in accordance with Section
8(b) of the Plan, the fair market value of the Common Stock; (ii) to determine
the exercise price per share of Options to be granted, which exercise price
shall be determined in accordance with Section 8(a) of the Plan; (iii) to
interpret the Plan; (iv) to prescribe, amend and rescind rules and regulations
relating to the Plan; (v) to authorize any person to execute on behalf of the
Company any instrument required to effectuate the grant of an Option previously
granted here-under; and (vi) to make: all other determinations deemed necessary
or advisable for the administration of the Plan.

          (d) Effect of Board's Decision. All decisions, determinations and
interpretations of the Board shall be final and binding on all Optionees and any
other holders of any Options granted under the Plan.

          (e) Suspension or Termination of Option. If the President or his or
her designee reasonably believes that an Optionee has committed an act of
misconduct, the President may suspend the Optionee's right to exercise any
option pending a determination by the Board of Directors (excluding the Outside
Director accused of such misconduct). If the Board of Directors (excluding the
Outside Director accused of such misconduct) determines an Optionee has
committed an act of embezzlement, fraud, dishonesty, nonpayment of an obligation
owed to the Company, breach of fiduciary duty or deliberate disregard of the
Company rules resulting in loss, damage or injury to the Company, or if an
Optionee makes an unauthorized disclosure of any Company trade secret or
confidential information, engages in any conduct constituting unfair
competition, induces any Company customer to breach a contract with the Company
or induces any principal for whom the Company acts as agent to terminate such
agency relationship, neither the Optionee nor his or her estate shall be
entitled to exercise any option whatsoever. In making such determination, the
Board

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of Directors (excluding the Outside Director accused of such misconduct) shall
act fairly and shall give the Optionee an opportunity to appear and present
evidence on Optionee's behalf at a hearing before the Board or a committee of
the Board.

     5. Eligibility. Options may be granted only to Outside Directors. All
Options shall be automatically granted in accordance with the terms set forth in
Section 4(b) hereof. An Outside Director who has been granted an Option may, if
he or she is otherwise eligible, be granted an additional Option or Options in
accordance with such provisions.

     The Plan shall not confer upon any Optionee any right with respect to
continuation of service as a Director or nomination to serve as a Director, nor
shall it interfere in any way with any rights which the Director or the Company
may have to terminate his or her directorship at any time.

     6. Term of Plan; Effective Date. The Plan shall become effective on the
date of its adoption by the Board of Directors of the Company. It shall continue
in effect for a term of ten (10) years unless sooner terminated under Section 13
of the Plan,

     7. Term of Option. The term of each Option shall be ten (10) years from the
date of grant thereof.

     8. 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 100% of the fair market value
per Share on the date of grant of the Option.

          (b) Fair Market Value. The fair market value shall be determined by
the Board in its discretion; provided, however, that where there is a public
market for the Common Stock, the fair market value per Share shall be the mean
of the bid and asked prices of the Common Stock in the over-the-counter market
on the date of grant, as reported in The Wall Street Journal (or, if not so
reported, as otherwise reported by the National Association of Securities
Dealers Automated Quotation ("NASDAQ" System) or, in the event the Common Stock
is traded on the NASDAQ National Market or listed on a stock exchange, the fair
market value per Share shall be the closing price on such system or exchange on
the date of grant of the Option, as reported in The Wall Street Journal. With
respect to any Options granted hereunder concurrently with the initial
effectiveness of the Plan, the fair market value shall be equal to the initial
public offering price of the Company's Common Stock as set forth on the cover
page of the prospectus relating to such initial public offering.

          (c) Form of Consideration. The consideration to be paid for the Shares
to be issued upon exercise of an Option shall consist entirely of cash, check,
other Shares of Common Stock having 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 (which, if acquired from the Company, shall have been held
for at least six months), or any combination of such methods of payment and/or
any other consideration or method of payment as shall be permitted under
applicable corporate law.

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     9. Exercise of Option.

          (a) Procedure for Exercise, Rights as a Shareholder. Any Option
granted hereunder shall be exercisable at such times as are set forth in Section
4(b) hereof, provided, however, that no Options shall be exercisable prior to
shareholder approved of the Plan in accordance with Section 17 hereof has been
obtained.

     An Option may not be exercised for a fraction of a Share.

     An Option shall be deemed to be exercised when written notice of such
exercise has been given to the Company in accordance with the terms of the
Option by the person entitled to exercise the Option and full payment for the
Shares with respect to which the Option is exercised has been received by the
Company. Full payment may consist of any consideration and method of payment
allowable under Section 8(c) of the Plan. 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 stock certificate evidencing such 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. A share certificate for the number of 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 the stock certificate is issued, except as provided in
Section 11 of the Plan.

     Exercise of an Option in any manner shall result in a decrease in the
number of Shares which thereafter may be 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 Status as a Director. If an Outside Director ceases
to serve as a Director, he or she may, but only within ninety (90) days (or such
other period of time not exceeding six (6) months as is determined by the Board)
after the date he or she ceases to be a Director of the Company, exercise his or
her Option to the extent that he or she was entitled to exercise it at the date
of such termination. Notwithstanding the foregoing, in no event may the Option
be exercised after its term set forth in Section 7 has expired. To the extent
that such Outside Director was not entitled to exercise an Option at the date of
such termination, or does not exercise such Option (which he or she was entitled
to exercise) within the time specified herein, the Option shall terminate.

          (c) Disability of Optionee. Notwithstanding Section 9(b) above, in the
event a Director is unable to continue his or her service as a Director with the
Company as a result of his or her total and permanent disability (as defined in
Section 22(e)(3) of the Internal Revenue Code), he or she may, but only within
six (6) months (or such other period of time not exceeding twelve (12) months as
is determined by the Board) from the date of such termination, exercise his or
her Option to the extent he or she was entitled to exercise it at the date of
such termination. Notwithstanding the foregoing, in no event may the Option be
exercised after its term set forth in Section 7 has expired. To the extent that
he or she was not entitled to exercise the Option at the date of termination, or
if he

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or she does not exercise such Option (which he or she was entitled to exercise)
within the time specified herein, the Option shall terminate.

          (d) Death of Optionee. In the event of the death of an Optionee:

               (i) During the term of the Option who is, at the time of his or
her death, a Director of the Company and who shall have been in Continuous
Status as a Director since the date of grant of the Option, the Option may be
exercised, at any time within six (6) months (or such lesser period of time as
is determined by the Board) following the date of death, by the Optionee's
estate or by a person who acquired the right to exercise the Option by bequest
or inheritance, but only to the extent of the right to exercise that would have
accrued had the Optionee continued living and remained in Continuous Status as
Director for six (6) months (or such lesser period of time as is determined by
the Board) after the date of death. Notwithstanding the foregoing, in no event
may the Option be exercised after its term set forth in Section 7 has expired.

               (ii) Within three (3) months (or such lesser period of time as is
determined by the Board) after the termination of Continuous Status as a
Director, the Option may be exercised, at any time within six (6) months
following the date of death, by the Optionee's estate or by a person who
acquired the right to exercise the Option by bequest or inheritance, but only to
the extent of the right to exercise that had accrued at the date of termination.
Notwithstanding the foregoing, in no event may the option be exercised after its
term set forth in Section t has expired.

     10. Nontransferability of Options. The 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. The designation of a beneficiary
by an Optionee does not constitute a transfer. An Option may be exercised during
the lifetime of an Optionee only by the Optionee or a transferee permitted by
this Section.

     11. Adjustments Upon Changes in Capitalization or Corporate Transactions.

          (a) Adjustment. 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

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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) Change of Ownership. In die event of (i) a dissolution or
liquidation of the Company, (ii) a sale of all or substantially all of the
Company's assets, (iii) a merger or consolidation in which the Company is not
the surviving corporation, or (iv) any other capital reorganization in which
more than fifty percent (50%) of the shares of the Company entitled to vote are
exchanged, the Company shall give to the Outside Director, at the time of
adoption of the plan for liquidation, dissolution, sale, merger, consolidation
or reorganization, either a reasonable time thereafter within which to exercise
the Option, prior to the effectiveness of such liquidation, dissolution, sale,
merger, consolidation or reorganization, at the end of which time the Option
shall terminate, or the right to exercise the Option (or receive a substitute
option with comparable terms) as to an equivalent number of shares of stock of
the corporation succeeding the Company or acquiring its business by reason of
such liquidation, dissolution, sale, merger, consolidation or reorganization.

     12. Time of Granting Options. The date of grant of an Option shall, for all
purposes, be the date determined in accordance with Section 4(b) hereof. Notice
of the determination shall be given to each Outside Director to whom an Option
is so granted within a reasonable time after the date of such grant.

     13. Amendment and Termination of the Plan.

          (a) Amendment and Termination. The Board may amend or terminate the
Plan from time to time in such respects as the Board may deem advisable;
provided that, to the extent necessary and desirable to comply with Rule 16b-3
under the Exchange Act (or any other applicable law or regulation), the Company
shall obtain approval of the shareholders of the Company to Plan amendments to
the extent and in the manner required by such law or regulation. Notwithstanding
the foregoing, the provisions set forth in Section 4 of this Plan (and any other
Sections of this Plan that affect the formula award terms required to be
specified in this Plan by Rule 16b-3) shall not be amended more than once every
six months, other than to comport with changes in the Code, the Employee
Retirement Income Security Act of 1974, as amended, or the rules thereunder.

          (b) Effect of Amendment or Termination. Any such amendment or
termination of the Plan that would impair the rights of any Optionee shall not
affect Options already granted to such Optionee and such Options shall remain in
full force and effect as if this Plan had not been amended or terminated, unless
mutually agreed otherwise between the Optionee and the Board, which agreement
must be in writing and signed by the Optionee and the Company.

     14. Conditions Upon Issuance of Shares.

          (a) 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 pursuant thereto shall comply with all relevant provisions of law,
including, without limitation, the Securities Act of 1933, as amended, the
Exchange Act, the rules and regulations promulgated thereunder, state

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securities laws, and the requirements of any stock exchange upon which the
Shares may then be listed, and shall be further subject to the approval of
counsel for the Company with respect to such compliance.

          (b) Condition to Exercise. As a condition to the exercise of an
Option, the Company may require the person exercising such Option to represent
and wan-ant 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 by any of the aforementioned relevant provisions of law.

          (c) No Liability. 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.

     15. 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.

     16. Option Agreement. Options shall be evidenced by written option
agreements in such form as the Board shall approve.

     17. Shareholder Approval. Continuance of the Plan shall- be subject to
approval by le shareholders of the Company at or prior to the first annual
meeting of shareholders held subsequent to the granting of an Option hereunder.
If such shareholder approval is obtained at a duly held shareholders' meeting,
it may be obtained by the affirmative vote of the holders of a majority of the
outstanding shares of the Company present or represented and entitled to vote
thereon. Options may be granted, but not exercised, before such shareholder
approval, If the shareholders fail to approve Us Plan within the required time
period, any Options granted under this Plan shall be void, and no additional
options shall be granted.

     18. Additional Restrictions of Rule 16b-3. The terms and conditions of
Options granted hereunder shall comply with the applicable provisions of Rule
16b-3. This Plan and the Options granted hereunder shall be deemed to contain
such additional conditions and restrictions as may be required for this Plan to
qualify as a "formula plan" under Rule 16b-3, as then applicable to the Company,
and to qualify for the maximum exemptions from Section 16 of the Exchange Act
with respect to Plan transactions.

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                                                                    EXHIBIT 10.3

                          1999 ISOCOR STOCK OPTION PLAN

        1. PURPOSES OF THE PLAN. The purposes of this Stock Option Plan are to
attract and retain the best available personnel for positions of substantial
responsibility, to provide additional incentive to the Employees and Consultants
of the Company and to promote the success of the Company's business.

               Options granted hereunder may be either Incentive Stock Options
(as defined under Section 422 of the Code) or Nonstatutory Stock Options, at the
discretion of the Board and as reflected in the terms of the written option
agreement.

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

               (a) "Administrator" shall mean the Board or any of its Committees
appointed pursuant to Section 4 of the Plan.

               (b) "Affiliate" shall mean an entity other than a Subsidiary (as
defined below) in which the Company owns an equity interest.

               (c) "Applicable Laws" shall mean the legal requirements relating
to the administration of stock option and restricted stock purchase plans under
applicable U.S. state corporate laws, U.S. federal and applicable state
securities laws, the Code, any Stock Exchange rules or regulations and the
applicable laws of any other country or jurisdiction where Options are granted
under the Plan, as such laws, rules, regulations and requirements shall be in
place from time to time.

               (d) "Board" shall mean the Board of Directors of the Company.

               (e) "Code" shall mean the Internal Revenue Code of 1986, as
amended.

               (f) "Committee" shall mean the Committee appointed by the Board
of Directors in accordance with Section 4(a) of the Plan, if one is appointed.

               (g) "Common Stock" shall mean the Common Stock of the Company.

               (h) "Company" shall mean Isocor, a California corporation.

               (i) "Consultant" means any person, including an advisor, who is
engaged by the Company or any Parent or Subsidiary to render services and is
compensated for such services, and any director of the Company whether
compensated for such services or not.

               (j) "Continuous Status as an Employee or Consultant" shall mean
the absence of any interruption or termination of service as an Employee or
Consultant. Continuous Status as an Employee or Consultant shall not be
considered interrupted in the case of sick leave, military leave, or any other
leave of absence approved by the Administrator; provided that such leave is for
a period of not more than 90 days or reemployment upon the expiration of such
leave is guaranteed by contract or statute. For purposes of this

<PAGE>   2

Plan, a change in status from an Employee to a Consultant or from a Consultant
to an Employee will not constitute a termination of employment.

               (k) "Director" shall mean a member of the Board.

               (l) "Employee" shall mean any person (including any Named
Executive, Officer or Director) employed by the Company or any Parent,
Subsidiary or Affiliate of the Company. The payment by the Company of a
director's fee to a Director shall not be sufficient to constitute "employment"
of such Director by the Company.

               (m) "Exchange Act" shall mean the Securities Exchange Act of
1934, as amended.

               (n) "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 National
Market of the National Association of Securities Dealers, Inc. Automated
Quotation ("Nasdaq") System, 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 system on the date of determination (or if no trading or bids occurred
on the date of determination, on the last trading day prior to the date of
determination), as such price is reported in The Wall Street Journal or such
other source as the Administrator deems reliable;

                    (ii) If the Common Stock is quoted on the Nasdaq System (but
not on the National Market thereof) or regularly quoted by a recognized
securities dealer but selling prices are not reported, its Fair Market Value
shall be the mean between the bid and asked prices for the Common Stock for the
last market trading day prior to the date of determination (or if no bids
occurred on the date of determination, on the last trading day prior to the date
of determination), as such prices are reported in the Wall Street Journal or
such other sources as the Administrator deems reliable; or

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

               (o) "Incentive Stock Option" shall mean an Option intended to
qualify as an incentive stock option within the meaning of Section 422 of the
Code, as designated in the applicable written option agreement.

               (p) "Named Executive" shall mean any individual who, on the last
day of the Company's fiscal year, is the chief executive officer of the Company
(or is acting in such capacity) or among the four highest compensated officers
of the Company (other than the chief executive officer). Such officer status
shall be determined pursuant to the executive compensation disclosure rules
under the Exchange Act.

               (q) "Nonstatutory Stock Option" shall mean an Option not intended
to qualify as an Incentive Stock Option, as designated in the applicable written
option agreement.

               (r) "Officer" shall mean 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.

               (s) "Option" shall mean a stock option granted pursuant to the
Plan.

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               (t) "Optioned Stock" shall mean the Common Stock subject to an
Option.

               (u) "Optionee" shall mean an Employee or Consultant who receives
an Option.

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

               (w) "Plan" shall mean this 1999 Stock Option Plan.

               (x) "Rule 16b-3" shall mean Rule 16b-3 promulgated under the
Exchange Act as the same may be amended from time to time, or any successor
provision.

               (y) "Share" shall mean a share of the Common Stock, as adjusted
in accordance with Section 14 of the Plan.

               (z) "Subsidiary" shall mean 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 14 of
the Plan, the maximum aggregate number of shares that may be sold under the Plan
is 350,000 shares of Common Stock, plus an automatic annual increase on the
first day of each fiscal year over the ten (10) year term of the Plan starting
in 2000 equal to 300,000 Shares of Common Stock. The Shares may be authorized,
but unissued, or reacquired Common Stock.

              If an Option should expire or become unexercisable for any reason
without having been exercised in full, the unpurchased Shares that were subject
thereto shall, unless the Plan shall have been terminated, become available for
future grant under the Plan. Notwithstanding any other provision of the Plan,
shares issued under the Plan and later repurchased by the Company shall not
become available for future grant under the Plan.

        4. ADMINISTRATION OF THE PLAN.

               (a) COMPOSITION OF ADMINISTRATOR.

                    (i) MULTIPLE ADMINISTRATIVE BODIES. If permitted by the
Applicable Laws, grants under the Plan may (but need not) be made by different
administrative bodies with respect to Directors, Officers who are not directors
and Employees who are neither Directors nor Officers.

                    (ii) ADMINISTRATION WITH RESPECT TO DIRECTORS AND OFFICERS.
With respect to grants of Options to Employees or Consultants who are also
Officers or Directors of the Company, grants under the Plan shall be made by (A)
the Board, if the Board may make grants under the Plan in compliance with Rule
16b-3 and Section 162(m) of the Code as it applies so as to qualify grants of
Options to Named Executives as performance-based compensation, or (B) a
Committee designated by the Board to make grants under the Plan, which Committee
shall be constituted in such a manner as to permit grants under the Plan to
comply with Rule 16b-3, to qualify grants of Options to Named Executives as
performance-based compensation under Section 162(m) of the Code and otherwise so
as to satisfy the Applicable Laws.

                    (iii) ADMINISTRATION WITH RESPECT TO OTHER PERSONS. With
respect to grants of Options to Employees or Consultants who are neither
Directors nor Officers of the

                                      -3-
<PAGE>   4

Company, the Plan shall be administered by (A) the Board or (B) a Committee
designated by the Board, which Committee shall be constituted in such a manner
as to satisfy the Applicable Laws.

                    (iv) GENERAL. If a Committee has been appointed pursuant to
subsection (ii) or (iii) of this Section 4(a), such Committee shall continue to
serve in its designated capacity until otherwise directed by the Board. From
time to time the Board may increase the size of any Committee and appoint
additional members thereof, remove members (with or without cause) and appoint
new members in substitution therefor, fill vacancies (however caused) and remove
all members of a Committee and thereafter directly administer the Plan, all to
the extent permitted by the Applicable Laws and, in the case of a Committee
appointed under subsection (ii), to the extent permitted by Rule 16b-3 and to
the extent required under Section 162(m) of the Code to qualify grants of
Options to Named Executives as performance-based compensation.

               (b) POWERS OF THE ADMINISTRATOR. Subject to the provisions of the
Plan and in the case of a Committee, 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,
in accordance with Section 2(n) of the Plan;

                    (ii) to select the Employees and Consultants to whom Options
may from time to time be granted hereunder;

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

                    (iv) to determine the number of shares of Common Stock to be
covered by each such award 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 (including, but not
limited to, the share price and any restriction or limitation, or any vesting
acceleration or waiver of forfeiture restrictions regarding any Option and/or
the shares of Common Stock relating thereto, based in each case on such factors
as the Administrator shall determine, in its sole discretion);

                    (vii) to determine whether and under what circumstances an
Option may be settled in cash under Section 10(g) instead of Common Stock;

                    (viii) 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.

               (c) EFFECT OF ADMINISTRATOR'S DECISION. All decisions,
determinations and interpretations of the Administrator shall be final and
binding on all Optionees and any other holders of any Options.

        5. ELIGIBILITY.

                                      -4-
<PAGE>   5

               (a) RECIPIENTS OF GRANTS. Nonstatutory Stock Options may be
granted to Employees and Consultants. Incentive Stock Options may be granted
only to Employees, provided, however, that Employees of an Affiliate shall not
be eligible to receive Incentive Stock Options. An Employee or Consultant who
has been granted an Option may, if he or she is otherwise eligible, be granted
an additional Option or Options.

               (b) TYPE OF OPTION. Each Option shall be designated in the
written option agreement as either an Incentive Stock Option or a Nonstatutory
Stock Option. However, notwithstanding such designations, to the extent that the
aggregate Fair Market Value of Shares with respect to which Incentive Stock
Options are exercisable for the first time by an Optionee during any calendar
year (under all plans of the Company or any Parent or Subsidiary) exceeds
$100,000, such excess Options shall be treated as Nonstatutory Stock Options.
For purposes of this Section 5(b), Incentive Stock Options shall be taken into
account in the order in which they were granted, and the Fair Market Value of
the Shares shall be determined as of the time the Option with respect to such
Shares is granted.

               (c) NO EMPLOYMENT RIGHTS. The Plan shall not confer upon any
Optionee any right with respect to continuation of employment or consulting
relationship with the Company, nor shall it interfere in any way with his or her
right or the Company's right to terminate his or her employment or consulting
relationship at any time, with or without cause.

        6. TERM OF PLAN. The Plan shall become effective upon its adoption by
the Board. It shall continue in effect for a term of ten (10) years unless
sooner terminated under Section 16 of the Plan.

        7. TERM OF OPTION. The term of each Option shall be the term stated in
the Option Agreement; provided, however, that in the case of an Incentive Stock
Option, the term shall be no more than ten (10) years from the date of grant
thereof or such shorter term as may be provided in the Option Agreement.
However, in the case of an Incentive Stock Option granted to an Optionee who, at
the time the Incentive Stock Option is granted, owns stock representing more
than ten percent (10%) of the voting power of all classes of stock of the
Company or any Parent or Subsidiary, the term of the Incentive Stock Option
shall be five (5) years from the date of grant thereof or such shorter term as
may be provided in the Option Agreement.

        8. LIMITATION ON GRANTS TO EMPLOYEES. Subject to adjustment as provided
in this Plan, the maximum number of Shares which may be subject to options
granted to any one Employee under this Plan for any fiscal year of the Company
shall be 750,000.

        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 such price as is
determined by the Administrator, but shall be subject to the following:

                    (i) In the case of an Incentive Stock Option

                         (A) granted to an Employee who, at the time of the
grant of such Incentive Stock Option, owns stock representing more than ten
percent (10%) of the voting power of all classes of stock of the Company or any
Parent or Subsidiary, the per Share exercise price shall be no less than 110% of
the Fair Market Value per Share on the date of grant; or

                                      -5-
<PAGE>   6

                         (B) granted to any other Employee, the per Share
exercise price shall be no less than 100% of the Fair Market Value per Share on
the date of grant.

                    (ii) In the case of a Nonstatutory Stock Option

                         (A) granted to a person who, at the time of the grant
of such Option, is a Named Executive of the Company, the per share Exercise
Price shall be no less than 100% of the Fair Market Value on the date of grant;
or

                         (B) granted to any person other than a Named Executive,
the per Share exercise price shall be no less than 85% of the Fair Market Value
per Share on the date of grant.

               (b) PERMISSIBLE CONSIDERATION. The consideration to be paid for
the Shares to be issued upon exercise of an Option, including the method of
payment, shall be determined by the Administrator (and, in the case of an
Incentive Stock Option, shall be determined at the time of grant) and may
consist entirely of (1) cash, (2) check, (3) promissory note, (4) other Shares
that (x) in the case of Shares acquired upon exercise of an Option either have
been owned by the Optionee for more than six months on the date of surrender or
were not acquired, directly or indirectly, from the Company, and (y) 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, (5) authorization from
the Company to retain from the total number of Shares as to which the Option is
exercised that number of Shares having a Fair Market Value on the date of
exercise equal to the exercise price for the total number of Shares as to which
the Option is exercised, (6) delivery of a properly executed exercise notice
together with irrevocable instructions to a broker to deliver promptly to the
Company the amount of sale or loan proceeds required to pay the exercise price,
(7) any combination of the foregoing methods of payment, or (8) such other
consideration and method of payment for the issuance of Shares to the extent
permitted under Applicable Laws. In making its determination as to the type of
consideration to accept, the Administrator shall consider if acceptance of such
consideration may be reasonably expected to benefit the Company.

        10. EXERCISE OF OPTION.

               (a) PROCEDURE FOR EXERCISE; RIGHTS AS A SHAREHOLDER. Any Option
granted hereunder shall be exercisable at such times and under such conditions
as determined by the Administrator, including performance criteria with respect
to the Company and/or the Optionee, and as shall be permissible under the terms
of the Plan.

                         An Option may not be exercised for a fraction of a
Share.

                         An Option shall be deemed to be exercised when written
notice of such exercise has been given to the Company in accordance with the
terms of the Option by the person entitled to exercise the Option and full
payment for the Shares with respect to which the Option is exercised has been
received by the Company. Full payment may, as authorized by the Administrator,
consist of any consideration and method of payment allowable under Section 9(b)
of the Plan. 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 stock certificate evidencing such 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 Company shall
issue (or cause to be issued) such stock certificate promptly upon exercise of
the Option. No adjustment will be made

                                      -6-
<PAGE>   7

for a dividend or other right for which the record date is prior to the date the
stock certificate is issued, except as provided in Section 13 of the Plan.

                    Exercise of an Option in any manner shall result in a
decrease in the number of Shares which thereafter may be 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 STATUS AS AN EMPLOYEE OR CONSULTANT. In the
event of termination of an Optionee's Continuous Status as an Employee or
Consultant, such Optionee may, but only within three (3) months (or such other
period of time, not exceeding three (3) months in the case of an Incentive Stock
Option, as is determined by the Administrator, with such determination in the
case of an Incentive Stock Option being made at the time of grant of the Option)
after the date of such termination (but in no event later than the date of
expiration of the term of such Option as set forth in the Option Agreement),
exercise his or her Option to the extent that he or she was entitled to exercise
it at the date of such termination. To the extent that the Optionee was not
entitled to exercise the Option at the date of such termination, or if the
optionee does not exercise such Option (which he or she was entitled to
exercise) within the time specified herein, the Option shall terminate.

               (c) DISABILITY OF OPTIONEE. Notwithstanding Section 10(b) above,
in the event of termination of an Optionee's Continuous Status as an Employee or
Consultant as a result of his or her total and permanent disability (as defined
in Section 22(e)(3) of the Code), he or she may, but only within twelve (12)
months from the date of such termination (but in no event later than the date of
expiration of the term of such Option as set forth in the Option Agreement),
exercise his or her Option to the extent he or she was entitled to exercise it
at the date of such termination. To the extent that he or she was not entitled
to exercise the Option at the date of termination, or if he does not exercise
such Option (which he was entitled to exercise) within the time specified
herein, the Option shall terminate.

               (d) DEATH OF OPTIONEE. In the event of the death of an Optionee
during the term of the Option who is at the time of his death an Employee or
Consultant of the Company and who shall have been in Continuous Status as an
Employee or Consultant since the date of grant of the Option, the Option may be
exercised, at any time within twelve (12) months, following the date of death
(but in no event later than the date of expiration of the term of such Option as
set forth in the Option Agreement), by the Optionee's estate or by a person who
acquired the right to exercise the Option by bequest or inheritance but only to
the extent the Optionee was entitled to exercise the Option at the date of
death.

               (e) EXTENSION OF EXERCISE PERIOD. The Administrator shall have
full power and authority to extend the period of time for which an Option is to
remain exercisable following termination of an Optionee's Continuous Service
Status from the periods set forth in Sections 10(b), 10(c) and 10(d) above or in
the Option Agreement to such greater time as the Administrator shall deem
appropriate, provided that in no event shall such Option be exercisable later
than the date of expiration of the term of such Option as set forth in the
Option Agreement.

               (f) RULE 16b-3. Options granted to persons subject to Section
16(b) of the Exchange Act must comply with Rule 16b-3 and shall contain such
additional conditions or restrictions as may be required thereunder to qualify
for the maximum exemption from Section 16 of the Exchange Act with respect to
Plan transactions.

                                      -7-
<PAGE>   8

               (g) BUY-OUT PROVISIONS. The Administrator may at any time offer
to buy out for a payment in cash or Shares an Option previously granted under
the Plan based on such terms and conditions as the Administrator shall establish
and communicate to the Optionee at the time such offer is made.

        11. TAXES.

               (a) As a condition of the exercise of an Option granted under the
Plan, the Optionee (or in the case of the Optionee's death, the person
exercising the Option) shall make such arrangements as the Administrator may
require for the satisfaction of any applicable federal, state, local or foreign
withholding tax obligations that may arise in connection with the exercise of
the Option and the issuance of Shares. The Company shall not be required to
issue any Shares under the Plan until such obligations are satisfied.

               (b) In the case of an Employee and in the absence of any other
arrangement, the Employee shall be deemed to have directed the Company to
withhold or collect from his or her compensation an amount sufficient to satisfy
such tax obligations from the next payroll payment otherwise payable after the
date of an exercise of the Option.

               (c) In the case of an Optionee other than an Employee (or in the
case of an Employee where the next payroll payment is not sufficient to satisfy
such tax obligations, with respect to any remaining tax obligations), in the
absence of any other arrangement and to the extent permitted under the
Applicable Laws, the Optionee shall be deemed to have elected to have the
Company withhold from the Shares to be issued upon exercise of the Option that
number of Shares having a Fair Market Value determined as of the applicable Tax
Date (as defined below) equal to the amount required to be withheld. For
purposes of this Section 11, the Fair Market Value of the Shares to be withheld
shall be determined on the date that the amount of tax to be withheld is to be
determined under the Applicable Laws (the "Tax Date").

               (d) If permitted by the Administrator, in its discretion, an
Optionee may satisfy his or her tax withholding obligations upon exercise of an
Option by surrendering to the Company Shares that (i) in the case of Shares
previously acquired from the Company, have been owned by the Optionee for more
than six (6) months on the date of surrender, and (ii) have a Fair Market Value
determined as of the applicable Tax Date equal to the amount required to be
withheld.

               (e) Any election or deemed election by an Optionee to have Shares
withheld to satisfy tax withholding obligations under Section 11(c) or (d) above
shall be irrevocable as to the particular Shares as to which the election is
made and shall be subject to the consent or disapproval of the Administrator.
Any election by an Optionee under Section 11(d) above must be made on or prior
to the applicable Tax Date.

               (f) In the event an election to have Shares withheld is made by
an Optionee and the Tax Date is deferred under Section 83 of the Code because no
election is filed under Section 83(b) of the Code, the Optionee shall receive
the full number of Shares with respect to which the Option is exercised but such
Optionee shall be unconditionally obligated to tender back to the Company the
proper number of Shares on the applicable Tax Date.

        12. NON-TRANSFERABILITY OF OPTIONS. The 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; provided that the Administrator
may in its discretion grant transferable Nonstatutory Stock Options pursuant to
option agreements specifying (i) the manner in which such Nonstatutory Stock
Options are transferable and (ii) that any such transfer shall be subject to the
Applicable Laws. The designation of a

                                      -8-
<PAGE>   9

beneficiary by an Optionee will not constitute a transfer. An Option may be
exercised, during the lifetime of the Optionee, only by the Optionee or a
transferee permitted by this Section 12.

        13. ADJUSTMENTS UPON CHANGES IN CAPITALIZATION; CORPORATE TRANSACTIONS.

               (a) ADJUSTMENT. Subject to any required action by the
shareholders of the Company, the number of shares of Common Stock covered by
each outstanding Option, the number of shares of Common Stock that 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, the maximum number of shares of Common Stock for which Options may
be granted to any employee under Section 8 of the Plan, and 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 Administrator, 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) CORPORATE TRANSACTIONS. In the event of the proposed
dissolution or liquidation of the Company, the Option will terminate immediately
prior to the consummation of such proposed action, unless otherwise provided by
the Administrator. The Administrator may, in the exercise of its sole discretion
in such instances, declare that any Option shall terminate as of a date fixed by
the Administrator and give each Optionee the right to exercise his or her Option
as to all or any part of the Optioned Stock, including Shares as to which the
Option would not otherwise be exercisable. In the event of a proposed sale of
all or substantially all of the assets of the Company, or the merger of the
Company with or into another corporation, the Option may be assumed or an
equivalent option may be substituted by such successor corporation or a parent
or subsidiary of such successor corporation. If the successor corporation does
not agree to assume the Option or substitute an equivalent option, the
Administrator shall notify the Optionee at least fifteen (15) prior to the
consummation of the transaction. To the extent it has not been previously
exercised, the Option will terminate immediately prior to the consummation of
such transaction.

        14. TIME OF GRANTING OPTIONS. The date of grant of an Option shall, for
all purposes, be the date on which the Administrator makes the determination
granting such Option or such other date as is determined by the Administrator;
provided however that in the case of any Incentive Stock Option, the grant date
shall be the later of the date on which the Administrator makes the
determination granting such Incentive Stock Option or the date of commencement
of the Optionee's employment relationship with the Company. Notice of the
determination shall be given to each Employee or Consultant to whom an Option is
so granted within a reasonable time after the date of such grant.

        15. AMENDMENT AND TERMINATION OF THE PLAN.

               (a) AMENDMENT AND TERMINATION. The Board may at any time amend,
alter, suspend, discontinue or terminate the Plan, but no amendment, alteration,
suspension, discontinuance or termination (other than an adjustment made
pursuant to Section 13 above) shall be made that would

                                      -9-
<PAGE>   10

materially and adversely affect the rights of any Optionee under any outstanding
grant, without his or her consent. In addition, to the extent necessary and
desirable to comply with the Applicable Laws, the Company shall obtain
stockholder approval of any Plan amendment in such a manner and to such as
degree as required.

               (b) EFFECT OF AMENDMENT OR TERMINATION. No amendment or
termination of the Plan shall materially and adversely affect Options already
granted, unless mutually agreed otherwise between the Optionee and the
Administrator, which agreement must be in writing and signed by such Optionee
and the Company.

        16. CONDITIONS UPON ISSUANCE OF SHARES. 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 pursuant thereto shall comply with all
relevant provisions of law, including, without limitation, the Securities Act of
1933, as amended, the Exchange Act, the rules and regulations promulgated
thereunder, and the requirements of any stock exchange upon which the Shares may
then be listed, and shall be further subject to the approval of counsel for the
Company with respect to such compliance.

               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 by any of
the aforementioned relevant provisions of law.

        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. 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.

        18. OPTION AGREEMENT. Options shall be evidenced by written option
agreements in such form as the Board shall approve.

        19. SHAREHOLDER APPROVAL. If required by the Applicable Laws,
continuance of the Plan shall be subject to approval by the shareholders of the
Company within twelve (12) months before or after the date the Plan is adopted.
Such shareholder approval shall be obtained in the manner and to the degree
required under the Applicable Laws.

                                      -10-
<PAGE>   11

                          1999 ISOCOR STOCK OPTION PLAN

                          NOTICE OF STOCK OPTION GRANT

Optionee's Name and Address:

        You have been granted an option to purchase Common Stock of ISOCOR (the
"Company") as follows:

        Board Approval Date:

        Date of Grant (Later of Board
               Approval Date or
               Commencement of
               Employment/Consulting):

        Exercise Price Per Share:

        Total Number of Shares Granted:

        Total Price of Shares Granted:

        Type of Option:                           Shares
                                                  Incentive Stock Option
                                                  Shares
                                                  Nonstatutory Stock Option

        Term/Expiration Date:

        Vesting Commencement Date:

        Vesting Schedule:                         1/4 of the original Shares
                                                  subject to this Option shall
                                                  vest one year after the
                                                  Vesting Commencement Date and
                                                  1/48th of the original number
                                                  of Shares subject to this
                                                  Option shall vest each month
                                                  thereafter.

        Termination Period:                       This Option may be exercised
                                                  for a period of 45 days after
                                                  termination of employment or
                                                  consulting relationship except
                                                  as set out in Sections 7 and 8
                                                  of the Stock Option Agreement
                                                  (but in no event later than
                                                  the Expiration Date).

<PAGE>   12

        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 ISOCOR 1999 Stock Option Plan and the Stock
Option Agreement, all of which are attached and made a part of this document.

OPTIONEE:                               ISOCOR

                                        By:
-----------------------------------         ------------------------------------
Signature

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

                                      -2-
<PAGE>   13

                                     ISOCOR

                             STOCK OPTION AGREEMENT

        1. GRANT OF OPTION. ISOCOR, a California corporation (the "Company"),
hereby grants to the Optionee named in the Notice of Stock Option Grant attached
to this Agreement ("Optionee"), an option (the "Option") to purchase the total
number of shares of Common Stock (the "Shares") set forth in the Notice of Stock
Option Grant, at the exercise price per share set forth in the Notice of Stock
Option Grant (the "Exercise Price") subject to the terms, definitions and
provisions of the 1999 Stock Option Plan (the "Plan") adopted by the Company,
which is incorporated in this Agreement by reference. In the event of a conflict
between the terms of the Plan and the terms of this Agreement, the terms of the
Plan shall govern. Unless otherwise defined in this Agreement, the terms used in
this Agreement shall have the meanings defined in the Plan.

               To the extent designated an Incentive Stock Option in the Notice
of Stock Option Grant, this Option is intended to qualify as an Incentive Stock
Option as defined in Section 422 of the Internal Revenue Code of 1986, as
amended (the "Code") and, to the extent not so designated, this Option is
intended to be a Nonstatutory Stock Option.

        2. EXERCISE OF OPTION. This Option shall be exercisable during its term
in accordance with the Vesting Schedule set out in the Notice of Stock Option
Grant and with the provisions of Sections 9 and 10 of the Plan as follows:

               (a) RIGHT TO EXERCISE.

                    (i) This Option may not be exercised for a fraction of a
share.

                    (ii) In the event of Optionee's death, disability or other
termination of employment, the exercisability of the Option is governed by
Sections 6, 7 and 8 below, subject to the limitations contained in paragraphs
(iii) and (iv) below.

                    (iii) In no event may this Option be exercised after the
date of expiration of the term of this Option as set forth in the Notice of
Stock Option Grant.

                    (iv) If designated an Incentive Stock Option in the Notice
of Stock Option Grant, in the event that the Shares subject to this Option (and
all other Incentive Stock Options granted to Optionee by the Company or any
Parent or Subsidiary) that vest in any calendar year have an aggregate fair
market value (determined for each Share as of the Date of Grant of the option
covering such Share) in excess of $100,000, the Shares in excess of $100,000
shall be treated as subject to a Nonstatutory Stock Option, in accordance with
Section 5 of the Plan.

               (b) METHOD OF EXERCISE.

                    (i) This Option shall be exercisable by delivering to the
Company a written notice of exercise (in the form attached as Exhibit A) which
shall state the election to exercise the Option, the number of Shares in respect
of which the Option is being exercised, and such other representations and
agreements as to the holder's investment intent with respect to such Shares of
Common Stock as may be required by the Company pursuant to the provisions of the
Plan. Such written notice shall be signed by

<PAGE>   14

Optionee and shall be delivered in person or by certified mail to the Stock
Option Administrator of the Company. The written notice shall be accompanied by
payment of the exercise price. This Option shall be deemed to be exercised upon
receipt by the Company of such written notice accompanied by the exercise price.

                    (ii) As a condition to the exercise of this Option, Optionee
agrees to make adequate provision for federal, state or other tax withholding
obligations, if any, which arise upon the exercise of the Option or disposition
of Shares, whether by withholding, direct payment to the Company, or otherwise.

                    (iii) No Shares will be issued pursuant to the exercise of
an Option unless such issuance and such exercise shall comply with all relevant
provisions of law and the requirements of any stock exchange upon which the
Shares may then be listed. Assuming such compliance, for income tax purposes the
Shares shall be considered transferred to Optionee on the date on which the
Option is exercised with respect to such Shares.

        3. OPTIONEE'S REPRESENTATIONS. In the event the Shares purchasable
pursuant to the exercise of this Option have not been registered under the
Securities Act of 1933, as amended (the "Securities Act"), at the time this
Option is exercised, Optionee shall, if required by the Company, concurrently
with the exercise of all or any portion of this Option, deliver to the Company
an investment representation statement in customary form, a copy of which is
available for Optionee's review from the Company upon request.

        4. METHOD OF PAYMENT. Payment of the exercise price shall be by any of
the following, or a combination of the following, at the election of Optionee:
(a) cash; (b) check; (c) surrender of other shares of Common Stock of the
Company that (i) either have been owned by Optionee for more than six (6) months
on the date of surrender or were not acquired, directly or indirectly, from the
Company, or (ii) 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; or (d) if there is a public market for the Shares and they are
registered under the Securities Act, delivery of a properly executed exercise
notice together with irrevocable instructions to a broker to deliver promptly to
the Company the amount of sale or loan proceeds required to pay the exercise
price.

        5. RESTRICTIONS ON EXERCISE. This Option may not be exercised until such
time as the Plan has been approved by the shareholders of the Company, or if the
issuance of such Shares upon such exercise or the method of payment of
consideration for such shares would constitute a violation of any applicable
federal or state securities or other law or regulation, including any rule under
Part 207 of Title 12 of the Code of Federal Regulations ("Regulation G") as
promulgated by the Federal Reserve Board. As a condition to the exercise of this
Option, the Company may require Optionee to make any representation and warranty
to the Company as may be required by any applicable law or regulation.

        6. TERMINATION OF RELATIONSHIP. In the event of termination of
Optionee's Continuous Status as an Employee or Consultant, Optionee may, to the
extent otherwise so entitled at the date of such termination (the "Termination
Date"), exercise this Option during the Termination Period set out in the Notice
of Stock Option Grant. To the extent that Optionee was not entitled to exercise
this Option at the date of such termination, or if Optionee does not exercise
this Option within the time specified in the Notice of Stock Option Grant, the
Option shall terminate.

        7. DISABILITY OF OPTIONEE. Notwithstanding the provisions of Section 6
above, in the event of termination of Optionee's Continuous Status as an
Employee or Consultant with the Company as a

                                      -2-
<PAGE>   15

result of total and permanent disability (as defined in Section 22(e)(3) of the
Code), Optionee may, but only within twelve (12) months from the date of
termination of employment or consultancy (but in no event later than the date of
expiration of the term of this Option as set forth in Section 10 below),
exercise the Option to the extent otherwise so entitled at the date of such
termination. To the extent that Optionee was not entitled to exercise the Option
at the date of termination, or if Optionee does not exercise such Option (to the
extent otherwise so entitled) within the time specified in this Agreement, the
Option shall terminate.

        8. DEATH OF OPTIONEE. In the event of the death of Optionee, the Option
may be exercised, at any time within six (6) months following the date of death
(but in no event later than the date of expiration of the term of this Option as
set forth in Section 10 below), by Optionee's estate or by a person who acquired
the right to exercise the Option by bequest or inheritance, but only to the
extent of the right to exercise that had accrued at the date of death.

        9. 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. The
designation of a beneficiary does not constitute a transfer. An Option may be
exercised during the lifetime of Optionee only by Optionee or a transferee
permitted by this section. The terms of this Option shall be binding upon the
executors, administrators, heirs, successors and assigns of Optionee.

        10. TERM OF OPTION. This Option may be exercised only within the term
set out in the Notice of Stock Option Grant, and may be exercised during such
term only in accordance with the Plan and the terms of this Option.

        11. NO ADDITIONAL EMPLOYMENT RIGHTS. Optionee understands and agrees
that the vesting of Shares pursuant to the Vesting Schedule is earned only by
continuing as an Employee or Consultant at the will of the Company (not through
the act of being hired, being granted this Option or acquiring Shares under this
Agreement). Optionee further acknowledges and agrees that nothing in this
Agreement, nor in the Plan which is incorporated in this Agreement by reference,
shall confer upon Optionee any right with respect to continuation as an Employee
or Consultant with the Company, nor shall it interfere in any way with his or
her right or the Company's right to terminate his or her employment or
consulting relationship at any time, with or without cause.

        12. TAX CONSEQUENCES. Optionee acknowledges that he or she has read the
brief summary set forth below of certain federal tax consequences of exercise of
this Option and disposition of the Shares under the law in effect as of the date
of grant. OPTIONEE UNDERSTANDS THAT THIS SUMMARY IS NECESSARILY INCOMPLETE, AND
THE TAX LAWS AND REGULATIONS ARE SUBJECT TO CHANGE. OPTIONEE SHOULD CONSULT HIS
OR HER OWN TAX ADVISER BEFORE EXERCISING THIS OPTION OR DISPOSING OF THE SHARES.

               (a) EXERCISE OF INCENTIVE STOCK OPTION. If this Option is an
Incentive Stock Option, there will be no regular federal income tax liability
upon the exercise of the Option, although the excess, if any, of the fair market
value of the Shares on the date of exercise over the Exercise Price will be
treated as an item of alternative minimum taxable income for federal tax
purposes and may subject Optionee to the alternative minimum tax in the year of
exercise.

               (b) EXERCISE OF NONSTATUTORY STOCK OPTION. If this Option does
not qualify as an Incentive Stock Option, Optionee may incur regular federal
income tax liability upon the exercise of the Option. Optionee will be treated
as having received compensation income (taxable at ordinary

                                      -3-
<PAGE>   16

income tax rates) equal to the excess, if any, of the fair market value of the
Shares on the date of exercise over the exercise price. In addition, if Optionee
is an employee of the Company, the Company will be required to withhold from
Optionee's compensation or collect from Optionee and pay to the applicable
taxing authorities an amount equal to a percentage of this compensation income
at the time of exercise.

               (c) DISPOSITION OF SHARES. If this Option is an Incentive Stock
Option and if Shares transferred pursuant to the Option are held for more than
one year after exercise and more than two years after the Date of Grant, any
gain realized on disposition of the Shares will be treated as long-term capital
gain for federal income tax purposes. If Shares purchased under an Incentive
Stock Option are disposed of before the end of either of such two holding
periods, then any gain realized on such disposition will be treated as
compensation income (taxable at ordinary income rates) to the extent of the
excess, if any, of the lesser of (i) the fair market value of the Shares on the
date of exercise, or (ii) the sales proceeds, over the exercise price. If this
Option is a Nonstatutory Stock Option, then gain realized on the disposition of
Shares will be treated as long-term or short-term capital gain depending on
whether or not the disposition occurs more than one year after the exercise
date. In the case of either an Incentive Stock Option or a Nonstatutory Stock
Option, the long-term capital gain will be taxed for federal income tax and
alternative minimum tax purposes at a maximum rate of 20%.

               (d) NOTICE OF DISQUALIFYING DISPOSITION. If the Option granted to
Optionee in this Agreement is an Incentive Stock Option, and if Optionee sells
or otherwise disposes of any of the Shares acquired pursuant to the Incentive
Stock Option on or before the later of (i) the date two years after the Date of
Grant, or (ii) the date one year after transfer of such Shares to Optionee upon
exercise of the Incentive Stock Option, Optionee shall notify the Company in
writing within thirty (30) days after the date of any such disposition. Optionee
agrees that Optionee may be subject to income tax withholding by the Company on
the compensation income recognized by Optionee from the early disposition by
payment in cash or out of the current earnings paid to Optionee.

        13. SIGNATURE. This Stock Option Agreement shall be deemed executed by
the Company and Optionee upon execution by such parties of the Notice of Stock
Option Grant attached to this Stock Option Agreement.

                  [Remainder of page left intentionally blank]

                                      -4-
<PAGE>   17

                                    EXHIBIT A

                               NOTICE OF EXERCISE

To:            ISOCOR

Attn:          Stock Option Administrator

Subject:       Notice of Intention to Exercise Stock Option

        This is official notice that the undersigned ("Optionee") intends to
exercise Optionee's option to purchase __________ shares of ISOCOR Common Stock,
under and pursuant to the Company's 1999 Stock Option Plan and the Notice of
Stock Option Grant and Stock Option Agreement dated ___________, as follows:

              Date of Grant :
                                                  ------------------------------
              Number of Shares:
                                                  ------------------------------
              Purchase Price:
                                                  ------------------------------
              Method of Payment
              of Purchase Price:
                                                  ------------------------------
        Social Security No.:
                               -------------------------------------------------
        The shares should be issued as follows:

               Name:
                               -------------------------------------------------
               Address:
                               -------------------------------------------------

                               -------------------------------------------------

                               -------------------------------------------------

                               -------------------------------------------------
               Signed:
                               -------------------------------------------------
               Date:
                               -------------------------------------------------

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