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                                                                    EXHIBIT 10.1


                                 ADDENDUM TO THE

                              EMPLOYMENT AGREEMENT

                                       OF

                                DANIEL L. MANACK


         THIS AMENDMENT is made this 1st day of May, 1999, by and between
HARBINGER CORPORATION, a Georgia corporation (the "Company"), and Daniel L.
Manack (the "Executive").

         A.       Purpose. The Executive is now employed by the Company pursuant
                  to an Employment Agreement dated December 4, 1996 (the
                  "Agreement") and the Company desires to provide an incentive
                  to the Executive to continue to devote his full attention and
                  undistracted dedication to the performance of his duties in
                  the potentially disturbing circumstances of a Change of
                  Control of the Company.

         B.       Severance Benefits and Limitations on Payment. If the
                  Executive's employment with the Company is terminated by the
                  Company other than for Cause or by the Executive for Good
                  Reason within the period beginning ninety (90) days before and
                  ending one hundred and eighty (180) days after a Change of
                  Control, (i) any stock options awarded the Executive which
                  remain outstanding and not vested as of the Date of
                  Termination shall be deemed vested and exercisable; provided
                  that acceleration in vesting does not adversely impact the
                  availability of pooling of interests accounting treatment, as
                  such determination is made by the Board in its reasonable
                  discretion, and (ii) the Executive will receive severance pay
                  equal to his annual base salary for six (6) months. However,
                  should the Executive's employment be terminated due to a
                  Change in Control within one year of the effective date of
                  this agreement, the severance pay will equal nine (9) months
                  of his annual base salary.

         C.       Definitions. For purposes of this Amendment, the following
                  definitions shall apply:

                  1.       Change of Control. A "Change of Control" shall be
                  conclusively deemed to have occurred if (and only if) any of
                  the following shall have taken place: (i) a Change of Control
                  is reported by the Company in response to either Item 6(e) of
                  Schedule 14A of Regulation 14A promulgated under the
                  Securities Exchange Act of 1934, as amended ("Exchange Act"),
                  or Item 1 of Form 8-K promulgated under the Exchange Act; (ii)
                  any person (as such term is used in Section 13(d) and 14(d)(2)
                  of the Exchange Act) is or becomes the beneficial owner (as
                  defined in Rule 13d-3 under the Exchange Act) directly


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                  or indirectly, of securities of the Company representing forty
                  percent (40%) or more of the combined voting power of the
                  Company's then outstanding securities; or (iii) following the
                  election or removal of directors, a majority of the Board
                  consists of individuals who were not members of the Board two
                  years before such election or removal, unless the election of
                  each director who was not a director at the beginning of such
                  two-year period has been approved in advance by directors
                  representing at least a majority of the directors then in
                  office who were directors at the beginning of the two-year
                  period.

                  2.       Date of Termination. "Date of Termination" means the
                  date on which a notice of termination is given either by the
                  Company or by the Executive.

                  3.       Good Reason. "Good Reason" means the Executive's
                  termination of employment for any of the following events,
                  unless such event occurs with the Executive's express prior
                  written consent:

                           (a)      The assignment to the Executive of any
                                    duties materially inconsistent with, or a
                                    diminution of, his position, duties, titles,
                                    offices, responsibilities and status with
                                    the Company as in effect immediately prior
                                    to the Change of Control of the Company,
                                    except in connection with the termination of
                                    the Executive's employment for disability,
                                    retirement, or Cause or as a result of the
                                    Executive's death or termination of
                                    employment other than for Good Reason;

                           (b)      A reduction in the Executive's base salary
                                    as in effect on the date of this Amendment
                                    or as the same may be increased from time to
                                    time;

                           (c)      A change in the location of the Executive's
                                    principal place of employment by more than
                                    seventy-five (75) miles from the location
                                    where he was principally employed
                                    immediately prior to the Change of Control;

                           (d)      Any material breach by the Company of any
                                    provision of this Amendment or the
                                    Agreement; or

                           (e)      Any failure by the Company to obtain the
                                    assumption of the Agreement by any successor
                                    or assign of the Company.

                  4.       Cause. "Cause" means termination of the Executive's
                  employment under any one or more of the following events:

                           (a)      Executive's knowing and willful misconduct
                                    with respect to the business and affairs of
                                    the Company;

                           (b)      Any material violation by Executive of any
                                    policy of the Company relating to ethical
                                    conduct or practices or fiduciary duties of
                                    a similarly situated executive;

                           (c)      Knowing and willful material breach of any
                                    provision of this Agreement which is not
                                    remedied within thirty (30) days after
                                    Executive's receipt of notice thereof;


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                           (d)      Executive's commission of a felony or any
                                    illegal act involving moral turpitude or
                                    fraud or Executive's dishonesty which may
                                    reasonably be expected to have a material
                                    adverse effect on the Company; and/or

                           (e)      Failure to comply with reasonable directives
                                    of the Board which are consistent with the
                                    Executive's duties, if not remedied within
                                    thirty (30) days after the Executive's
                                    receipt of notice thereof.

         IN WITNESS WHEREOF, the parties hereto have executed this Amendment as
of the 1st day of May, 1999.

HARBINGER CORPORATION:                      EMPLOYEE:


James M. Travers                            Daniel L. Manack
-----------------------------------         -----------------------------------
Name                                        Name


President & Chief Operating Officer         /s/ Daniel L. Manack
-----------------------------------         -----------------------------------
Title                                       Signature


/s/ James M. Travers
-----------------------------------
Signature