<PAGE>   1
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                                  UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                                    FORM 10-Q

[MARK ONE]

|X|      QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES
         EXCHANGE ACT OF 1934

                  FOR THE QUARTERLY PERIOD ENDED MARCH 31, 1999

                                       OR

|_|      TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES
         EXCHANGE ACT OF 1934

           FOR THE TRANSITION PERIOD FROM              TO
                                          ------------   ---------------

                         COMMISSION FILE NUMBER 0-26298

                              HARBINGER CORPORATION
             (Exact name of registrant as specified in its charter)

<TABLE>
<CAPTION>

      <S>                                                                <C>
                          GEORGIA                                                     58-1817306
      (State or other Jurisdiction of incorporation or                   (I.R.S. Employer Identification No.)
                       organization)


                 1277 LENOX PARK BOULEVARD                                              30319
                      ATLANTA, GEORGIA                                                (Zip Code)
          (Address of principal executive offices)
</TABLE>

       REGISTRANT'S TELEPHONE NUMBER, INCLUDING AREA CODE: (404) 467-3000

Indicate by check mark whether the Registrant (1) has filed all reports required
to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during
the preceding 12 months (or for such shorter period that the Registrant was
required to file such reports) and (2) has been subject to such filing
requirements for the past 90 days. Yes |X| No |_|

The number of shares of the issuer's class of capital stock outstanding as of
May 3, 1999, the latest practicable date, is as follows: 38,383,412 shares of
Common Stock, $.0001 par value.


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




<PAGE>   2



                              HARBINGER CORPORATION
                                    FORM 10-Q
                          QUARTER ENDED MARCH 31, 1999


                                TABLE OF CONTENTS
<TABLE>
<CAPTION>

                                                                                                    Page
                                                                                                   Number
                                                                                                -------------

<S>                                                                                             <C>
PART I.  FINANCIAL INFORMATION

Item 1.  Financial Statements

              Consolidated Balance Sheets - (Unaudited) March 31, 1999
                   and December  31, 1998.................................................

              Consolidated Statements of Operations (Unaudited) - Three
                  Months Ended March 31, 1999 and 1998....................................

              Consolidated Statements of Comprehensive Income (Loss) (Unaudited) -
                     Three Months Ended March 31, 1999 and 1998...........................

              Consolidated Statements of Cash Flows (Unaudited) -
                     Three Months Ended March 31, 1999 and 1998...........................

              Notes to Consolidated Financial Statements (Unaudited)......................


Item 2.  Management's Discussion and Analysis of Financial Condition and
              Results of Operations.......................................................


PART II.  OTHER INFORMATION

Item 4.  Submission of Matters to a Vote of Security Holders..............................

Item 6.  Exhibits and Reports on Form 8-K.................................................


PART III.  SIGNATURES.....................................................................
</TABLE>


<PAGE>   3


ITEM 1.  FINANCIAL STATEMENTS



                              HARBINGER CORPORATION
                           CONSOLIDATED BALANCE SHEETS
                                   (UNAUDITED)
                        (IN THOUSANDS, EXCEPT SHARE DATA)
<TABLE>
<CAPTION>

                                                                                    March 31,      December 31,
                                                                                      1999            1998
                                                                                   ----------      ------------
                                   ASSETS
<S>                                                                                <C>             <C>
Current assets:
   Cash and cash equivalents ................................................      $   14,109      $     33,059
   Short-term investments ...................................................          59,901            59,248
   Accounts receivable, less allowances for returns and
     doubtful accounts of  $5,458 at March 31, 1999
     and $5,464 at December 31, 1998 ........................................          32,469            35,891
   Royalties receivable, less allowance for doubtful accounts
     of $2,864 at March 31, 1999 and $3,614
     at December 31, 1998 ...................................................             681             1,730
   Deferred income taxes ....................................................           2,103             2,103
   Other current assets .....................................................           4,975             5,622
                                                                                   ----------      ------------
       Total current assets .................................................         114,238           137,653
                                                                                   ----------      ------------
   Property and equipment, less accumulated depreciation
     and amortization .......................................................          23,707            23,150
   Intangible assets, less accumulated amortization .........................          16,884            16,803
   Deferred income taxes ....................................................             698               698
   Other assets .............................................................             637                65
                                                                                   ----------      ------------
                                                                                   $  156,164      $    178,369
                                                                                   ==========      ============
                    LIABILITIES AND SHAREHOLDERS' EQUITY
Current liabilities:
   Accounts payable .........................................................      $    3,538      $      5,566
   Accrued expenses .........................................................          26,726            31,571
   Deferred revenues ........................................................          19,467            21,213
                                                                                   ----------      ------------
       Total current liabilities ............................................          49,731            58,350
                                                                                   ----------      ------------

Commitments and contingencies

Redeemable preferred stock:
   Zero coupon redeemable preferred stock, no par value; 2,000,000
     shares authorized, issued and outstanding ..............................               _                 _

Shareholders' equity:
   Preferred stock, no par value; 18,000,000 shares authorized;
     none issued or outstanding..............................................               _                 _
   Common stock, $0.0001 par value; 100,000,000 shares
     authorized, 42,439,760 shares and 42,313,031 shares issued
     as of  March 31, 1999 and December 31, 1998 ............................               4                 4
   Additional paid-in capital ...............................................         202,101           201,615
   Accumulated deficit ......................................................         (71,187)          (73,528)
    Accumulated other comprehensive loss ....................................          (1,257)             (622)
         Treasury stock, 4,056,050 shares as of March 31, 1999 and
         1,562,100 shares as of December 31, 1998 ...........................         (23,228)           (7,450)
                                                                                   ----------      ------------
              Total shareholders' equity ....................................         106,433           120,019
                                                                                   ----------      ------------
                                                                                   $  156,164      $    178,369
                                                                                   ==========      ============
</TABLE>

          See accompanying notes to consolidated financial statements.




<PAGE>   4





                              HARBINGER CORPORATION
                      CONSOLIDATED STATEMENTS OF OPERATIONS
                                   (UNAUDITED)
                      (IN THOUSANDS, EXCEPT PER SHARE DATA)
<TABLE>
<CAPTION>

                                                                              Three Months Ended
                                                                                   March 31,
                                                                             ---------------------
                                                                               1999         1998
                                                                             -------      --------
<S>                                                                          <C>          <C>
Revenues:
   Services ...........................................................      $25,372      $ 19,849
   Software ...........................................................        8,131        10,203
                                                                             -------      --------
     Total revenues ...................................................       33,503        30,052
                                                                             -------      --------

Direct costs:
   Services ...........................................................       10,626         7,033
   Software ...........................................................        1,131           771
                                                                             -------      --------
     Total direct costs ...............................................       11,757         7,804
                                                                             -------      --------

         Gross margin .................................................       21,746        22,248
                                                                             -------      --------

Operating costs:
   Selling and marketing ..............................................        8,183         6,612
   General and administrative .........................................        6,560         5,499
   Depreciation and amortization ......................................        2,233         1,875
   Product development ................................................        3,214         2,519
   Charge for purchased in-process product development,
     write-off of software development costs, restructuring,
     acquisition related and other charges ............................           --         8,039
                                                                             -------      --------
       Total operating costs ..........................................       20,190        24,544
                                                                             -------      --------
         Operating income (loss) ......................................        1,556        (2,296)

Interest income, net ..................................................          898         1,311
                                                                             -------      --------
           Income (loss) from continuing operations before income taxes        2,454          (985)
Income tax expense ....................................................          113           136
                                                                             -------      --------
         Income (loss) from continuing operations .....................        2,341        (1,121)
Loss from discontinued operations .....................................           --          (217)
                                                                             -------      --------
         Net income (loss) applicable to common shareholders ..........      $ 2,341      $ (1,338)
                                                                             =======      ========


Basic earnings per common share:
   Income (loss) from continuing operations ...........................      $  0.06      $  (0.03)
   Income (loss) from discontinued operations .........................           --            --
                                                                             -------      --------
       Net income (loss) per common share .............................      $  0.06      $  (0.03)
                                                                             =======      ========

Weighted average number of common shares outstanding
                                                                              39,879        41,046
                                                                             =======      ========

Earnings per common share assuming dilution:
   Income (loss) from continuing operations ...........................      $  0.06      $  (0.03)
   Income (loss) from discontinued operations .........................           --            --
                                                                             -------      --------
       Net income (loss) per common share .............................      $  0.06      $  (0.03)
                                                                             =======      ========

Weighted average number of common shares outstanding assuming
   dilution ...........................................................       40,451        41,046
                                                                             =======      ========
</TABLE>




          See accompanying notes to consolidated financial statements.


<PAGE>   5



                              HARBINGER CORPORATION
             CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS)
                                   (UNAUDITED)
                                 (IN THOUSANDS)

<TABLE>
<CAPTION>

                                                             Three Months Ended
                                                                 March 31,
                                                            ---------------------
                                                             1999          1998
                                                            -------       -------

   <S>                                                      <C>           <C>
   Net income (loss) applicable to common shareholders      $ 2,341       $(1,338)
   Other comprehensive loss, net of tax:
     Foreign currency translation adjustments ........         (635)         (205)
                                                            -------       -------

       Comprehensive income (loss) ...................      $ 1,706       $(1,543)
                                                            =======       =======
</TABLE>




          See accompanying notes to consolidated financial statements.


<PAGE>   6


                              HARBINGER CORPORATION
                      CONSOLIDATED STATEMENTS OF CASH FLOWS
                                   (UNAUDITED)
                                 (IN THOUSANDS)
<TABLE>
<CAPTION>

                                                                     Three Months Ended
                                                                         March 31,
                                                                  -----------------------
                                                                    1999           1998
                                                                  --------       --------

<S>                                                               <C>            <C>
Cash flows provided by operating activities ................      $    454       $  1,150

Cash flows from investing activities:
   Net (purchases) redemption  of short-term investments ...          (653)         1,066
   Purchases of property and equipment .....................        (2,378)        (2,545)
   Additions to software development costs .................          (887)          (869)
                                                                  --------       --------
         Net cash used in investing activities .............        (3,918)        (2,348)
                                                                  --------       --------

Cash flows from financing activities:
   Exercise of stock options and warrants and issuance of
     stock under employee stock purchase plan ..............           486          6,746
   Purchases of common stock ...............................       (15,778)            --
   Principal payments under notes payable and long-term debt            --           (169)
                                                                  --------       --------
         Net cash provided by (used in) financing activities       (15,292)         6,577
                                                                  --------       --------
Net increase (decrease) in cash and cash equivalents .......       (18,756)         5,379
Cash and cash equivalents at beginning of period ...........        33,059         69,811
Effect of exchange rates on cash held in foreign currencies           (194)            12
Cash received from acquisitions ............................            --             52
                                                                  --------       --------
Cash and cash equivalents at end of period .................      $ 14,109       $ 75,254
                                                                  ========       ========

Supplemental disclosures:
   Cash paid for interest ..................................      $     --       $     25
                                                                  ========       ========
   Cash paid for income taxes ..............................      $     45       $    347
                                                                  ========       ========
</TABLE>



          See accompanying notes to consolidated financial statements.



<PAGE>   7



                              HARBINGER CORPORATION
                   NOTES TO CONSOLIDATED FINANCIAL STATEMENTS
                                 MARCH 31, 1999
                                   (UNAUDITED)


1.       SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

         BASIS OF PRESENTATION

         The accompanying unaudited consolidated financial statements have been
prepared in accordance with generally accepted accounting principles for interim
financial information and with the instructions to Form 10-Q. Accordingly, they
do not include all of the information and footnotes required by generally
accepted accounting principles for complete financial statements. The financial
information included herein is unaudited; however, the information reflects all
adjustments (consisting solely of normal recurring adjustments) that are, in the
opinion of management, necessary to a fair presentation of the financial
position, results of operations, and cash flows for the interim periods.
Operating results for the three months ended March 31, 1999 are not necessarily
indicative of the results that may be expected for the year ended December 31,
1999. For further information, refer to the financial statements and footnotes
thereto included in Harbinger Corporation's ("Harbinger" or the "Company") Form
10-K for the year ended December 31, 1998 and the Company's current report on
Form 8-K dated April 2, 1999.

         RECLASSIFICATIONS

         Certain reclassifications have been made to the quarter ended March 31,
1998 unaudited consolidated financial statements to conform with the
presentation of quarter ended March 31, 1999.

         SEGMENT REPORTING

         On December 31, 1998, the Company adopted Statement of Financial
Accounting Standards No. 131, Disclosures about Segments of an Enterprise and
Related Information, issued by the FASB in June 1997, effective for fiscal years
beginning after December 15, 1997.

2.       SHAREHOLDERS' EQUITY

         On March 22, 1999 the Board of Directors approved the purchase of an
additional 10% of the Company's outstanding shares of common stock under its
existing stock repurchase program. The Company completed the 10% repurchase
authorized on October 2, 1998 on March 19, 1999.

3.       CHARGE FOR PURCHASED IN-PROCESS PRODUCT DEVELOPMENT, WRITE-OFF OF
         SOFTWARE DEVELOPMENT COSTS, RESTRUCTURING, ACQUISITION RELATED AND
         OTHER CHARGES

         For the quarter ended March 31, 1999, the Company did not incur charges
for purchased in-process product development, write-off of software development
costs, restructuring, acquisition related and other charges ("Charges"). A
summary of the Charges incurred in the quarter ended March 31, 1998 is as
follows:


<TABLE>
<CAPTION>

                                                                       Three Months
                                                                      Ended March 31,
                                                                           1998
                                                                        ---------
                <S>                                               <C>
                Integration costs ...............................       $   6,380
                Transaction charges..............................             388
                Asset write downs................................             151
                Severance costs..................................           1,120
                                                                        ---------
                                                                        $   8,039
                                                                        =========
</TABLE>


<PAGE>   8
 
         Approximately $2.0 million of the Charges incurred in the three months
ended March 31, 1998 resulted from the redirection of internal resources and
their associated costs ("Integration Activity Costs") to manage integration
activities. In 1999 the management of these activities has been completed and
these internal resources and their associated costs are therefore recorded to
their original operation expense categories.

         At March 31, 1999 the accrued liabilities related to Charges were
approximately $5.8 million, compared to approximately $7.5 million at December
31, 1998, primarily as a result of charges to the reserve for leases, severance
costs, professional fees and payments to customers of phased-out products in
lieu of continued service obligations on those contracts.  Certain Charges
involve management estimates, as follows: lease termination costs and other
costs to exit activities, which include anticipated liabilities and obligations
associated with phasing out products. Actual results could vary from these
estimates.

4.       INCOME TAXES

         The Company reduced its valuation allowance in the quarter ended March
31, 1999 by $844,000. This relates to the reduction in the gross deferred income
tax assets that are realized through reversals of existing deductible temporary
differences. The Company continually reviews the adequacy of the valuation
allowance and recognizes these benefits as reassessment indicates it is more
likely than not that the benefits will be realized.


5.       DISCONTINUED OPERATIONS

         In the third quarter of 1998 the Board of Directors approved the
discontinuance of the TrustedLink Procurement business ("TLP"), expected to be
sold or liquidated within 12 months. The results of operations for the TLP
business for all periods prior to the discontinuation date of September 30, 1998
are reported in the accompanying consolidated statements of operation under
"loss from discontinued operations". Revenues from TLP were $29,000 and $1.0
million for the three-month periods ended March 31, 1999 and 1998, respectively.
The Company provided for an estimated anticipated loss on the future disposal of
TLP, including an estimate for operating losses during the phase-out period, of
$6.4 million at September 30, 1998. The balance of the loss reserve at March 31,
1999 was $4.7 million after $455,000 in operating losses in the first quarter of
1999. The anticipated loss on the disposal of TLP contains certain management
estimates, included but not limited to sales proceeds, lease exist costs and
length of operations beyond the measurement date. Actual results could vary from
such estimates. No income tax benefit was recognized in any period due to the
Company's net operating loss carry forwards. The operating loss incurred for TLP
from the measurement date to March 31, 1999 was $1.1 million.

The assets and liabilities of TLP are included in the Company's consolidated
balance sheets as follows:

<TABLE>
<CAPTION>

                                           March 31,     December 31,
                                              1999           1998
                                           ---------     ------------
          <S>                              <C>           <C>
          Accounts receivable              $     380     $        454
          Other current assets                   102              106
          Property and equipment, net            766              766
          Intangible assets, net               2,454            2,454
          Deferred revenue                       (26)             (45)
          Current liabilities                   (345)            (281)
                                           ---------     ------------
                   Net Assets              $   3,331     $      3,454
                                           =========     ============
</TABLE>

<PAGE>   9

6.       RELATED PARTY TRANSACTIONS

         The Company received notes receivable during the first quarter of 1999
of $605,000 from five former shareholders of EDI Works! LLC., an immaterial
pooling of interests acquisition completed in 1998. The terms of the notes are
for 18 months with an annual interest rate of 8.75%. Interest accrues on a
monthly basis with principal and interest due at the end of the notes.

7.       SEGMENT INFORMATION

         The Company operates in a single industry segment: the development,
marketing and supporting of software products and the providing of network and
consulting services to enable businesses to engage in E-Commerce. The Company
manages its business along geographical lines, thus resulting in three
reportable segments: North America, Europe, and Asia Pacific and Latin America.
The accounting policies of each segment are the same as those described in the
summary of significant accounting policies. Revenues are attributed to a
reportable segment based on the location of the customer. Management evaluates
the performance of each segment on the basis of operating income, excluding
integration and restructuring charges and certain general and administrative
credits. Intersegment royalties are calculated based upon revenues, as defined,
derived from the sales of certain software products and services at agreed upon
percentages between the segments.

         A summary of the Company's reportable segments as of March 31, 1999 and
March 31, 1998 is presented below (in thousands):

<TABLE>
<CAPTION>

                                                       North                              Latin
                                                      America            Europe          America           Total
                                                                                     & Asia Pacific
                                                    ----------           -------     ---------------      ---------
<S>                                                 <C>                  <C>               <C>            <C>
Revenues:
     1999                                           $   28,413           $ 5,729           $  511         $ 34,653
     1998                                           $   25,311           $ 5,096           $  398         $ 30,805
Intersegment Royalties:
     1999                                           $    1,150           $     -           $    -         $  1,150
     1998                                           $      753           $     -           $    -         $    753
Operating Income (as defined):
     1999                                           $       54           $   833           $  (81)        $    806
     1998                                           $    5,380           $   231           $  132         $  5,743
</TABLE>


<TABLE>
<CAPTION>


                                                       1999            1998
                                                     --------        --------
<S>                                                  <C>             <C>
Revenues:
---------
Total gross revenues for reportable segments         $ 34,653        $ 30,805
Elimination of intersegment royalties                  (1,150)           (753)
                                                     --------        --------
   Total consolidated revenues                       $ 33,503        $ 30,052
                                                     ========        ========

                                                         1999            1998
                                                     --------        --------

Operating Income (as defined):
------------------------------
Total operating income for reportable segments       $    806        $  5,743
Charges for integration and restructuring                  --          (8,039)
Certain general and administrative credits                750              --
                                                     --------        --------
   Total consolidated operating income (loss)        $  1,556        $ (2,296)
                                                     ========        ========
</TABLE>


<PAGE>   10


8.       CONTINGENCIES

         The Company is involved in claims and other legal actions arising out
of the ordinary course of business. While the ultimate results and outcome
cannot be determined, management does not expect that they will have a material
adverse effect on the Company's results of operations or financial position.

ITEM 2. MANAGEMENT'S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS
OF OPERATIONS

         The following discussion and analysis should be read in conjunction
with the consolidated financial statements and notes thereto included elsewhere
herein and the Company's Form 10-K for the year ended December 31, 1998 and the
Company's current report on Form 8-K dated April 2, 1999.

OVERVIEW

         Harbinger Corporation (the "Company") generates revenues from various
sources, including revenues for services and license fees and royalties for
software. Revenues for services principally include subscription fees for
transactions on Harbinger.net, the Company's electronic commerce portal,
software maintenance and implementation charges and professional service fees
for consulting and training services. Subscription fees are based on a
combination of monthly access charges and transaction-based usage charges and
are recognized based on actual charges incurred each month. Software maintenance
and implementation revenues represent recurring charges to customers and are
deferred and recognized ratably over the service period. Revenues for
professional services are based on actual services rendered and are recognized
as services are performed. License fees for software are generally recognized
upon shipment, net of estimated returns. Software revenues also include royalty
revenues under distribution agreements with third parties which are recognized
either on shipment of software to a distributor or upon sales to end users by a
distributor depending on the terms of the distribution agreement.

RESULTS OF OPERATIONS

REVENUES

         Total revenues increased 11% to $33.5 million in the three months ended
March 31, 1999 from $30.1 million in the same period in 1998. Revenues for
services increased 28% to $25.4 million in the three months ended March 31, 1999
from $19.8 million in the same period in 1998, reflecting increases in
professional services and maintenance revenues.

         Revenues from software license fees decreased 20% to $8.1 million in
the three months ended March 31, 1999 from $10.2 million in the same period in
1998. The decrease in 1999 compared to 1998 was primarily attributable to the
phase-out of certain non-strategic software products ("Sunset Products") and a
reduction in the fees received from third party resellers of the Company's
software products.
<PAGE>   11

DIRECT COSTS

         Direct costs for services increased to $10.6 million in the three
months ended March 31, 1999 from $7.0 million in the three months ended March
31, 1998. As a percentage of services revenues, these costs were 41.9% for the
three months ended March 31, 1999 and 35.4% for the three months ended March 31,
1998. The increase in direct costs as a percentage of services revenues for the
first quarter of 1999 compared to the first quarter of 1998 primarily reflects
the effects of a higher mix of professional services revenues in the first
quarter of 1999 and the effect of reallocating costs to Integration Activity
Costs in 1998.

         Direct software costs increased to $1.1 million for the three months
ended March 31, 1999 from $771,000 for the three months ended March 31, 1998.
Direct software costs as a percentage of software revenues were 13.9% for the
three months ended March 31, 1999 and 7.6% for the three months ended March 31,
1998. The increase in direct software costs as a percentage of software revenues
for the first quarter of 1999 compared to the first quarter of 1998 primarily
reflects the effects of increased amortization of capitalized software for
certain newly released products, and to a lesser extent, write-off of outdated
collateral materials, accompanied by the decreased revenues from Sunset
Products.

SELLING AND MARKETING

         Selling and marketing expenses increased 24% to $8.2 million, or 24.4%
of revenues in the three months ended March 31, 1999, from $6.6 million, or
22.0% of revenues in the three months ended March 31, 1998. The increase in
selling and marketing expenses as a percentage of revenues is primarily due to
increased marketing programs in 1999 and the effect of reallocating costs to
Integration Activity Costs in 1998.

GENERAL AND ADMINISTRATIVE

         General and administrative expenses increased 19% to $6.6 million in
the three months ended March 31, 1999 from $5.5 million in the three months
ended March 31, 1998. As a percentage of revenues, these expenses increased to
19.6% of revenues in the three months ended March 31, 1999 from 18.3% of
revenues in the three months ended March 31, 1998. The 1999 period includes a
credit of $750,000 due to the receipt of an outstanding royalty receivable from
a specific customer that had been written off in 1998. If this receipt had not
occurred, general and administrative expenses would have been $7.3 million or
21.8% of revenues. The increase as a percentage of revenues is attributed to the
effect of reallocating costs to Integration Activity Costs in 1998, and an
increase in office space to accommodate expansion, an increase in infrastructure
investments, principally in the Information Technology area, and an increase in
compensation-related accruals in 1999.

DEPRECIATION AND AMORTIZATION

         Depreciation and amortization increased 19% to $2.2 million in the
three months ended March 31, 1999 from $1.9 million in the three months ended
March 31, 1998. As a percentage of revenues, these expenses were 6.7% for the
first quarter of 1999 and 6.2% for the first quarter of 1998. The increase in
depreciation and amortization for the three months ended March 31, 1999 compared
to 1998 is primarily associated with the purchase of computer hardware and
software associated with the Company's increased investments in its information
technology infrastructure.

   PRODUCT DEVELOPMENT

         Total expenditures for product development, including capitalized
software development costs, increased to $4.1 million for the three months ended
March 31, 1999 from $3.4 million for the three months ended March 31, 1998.
Total expenses for product development increased to $3.2 million, for the three
months ended March 31, 1999 from $2.5 million compared to the same period of
1998. As a percentage of revenues total product development expenses increased
to 9.6% in the three months ended March 31, 1999 from 8.4% in the same period of
1998. The increase in 1999 is due to increased development of internet based
products and the effect of reallocating costs to Integration Activity Costs in
1998. The Company capitalized software costs of $887,000 in 1999 and $869,000 in
1998.
<PAGE>   12

CHARGE FOR PURCHASED IN-PROCESS PRODUCT DEVELOPMENT, WRITE-OFF OF SOFTWARE
DEVELOPMENT COSTS, RESTRUCTURING, ACQUISITION RELATED AND OTHER CHARGES
("CHARGES")

         The Company incurred Charges of $27.0 million during the year ended
December 31, 1998 relating to the costs of integrating its acquisition in 1998
and 1997 and restructuring in 1998. Approximately $4.1 million of the Charges
consisted of an allocation of internal costs associated with personnel who
performed integration-related activities associated with these acquisitions
("Integration Activity Costs"). The integration activities were completed by the
end of 1998 and the internal resources and their associated costs may recur in
their original expense categories in 1999.

         For the quarters ended March 31, 1999 and 1998, the Company incurred $0
and $8.0 million, respectively, in Charges, of which $2.0 million in 1998 was
costs reclassified internally as Integration Activity Costs. (See Note 3 to the
accompanying unaudited consolidated financial statements.)

INTEREST INCOME, NET

         Interest income, net, decreased 31% to $898,000 for the three months
ended March 31, 1999 from $1.3 million for the three months ended March 31, 1998
as a result of spending approximately $15.8 million to acquire common stock of
the Company authorized in its on-going repurchase program.

INCOME TAXES

         The Company recorded lower income tax expense of $113,000 for the three
months ended March 31, 1999 as compared to $136,000 for the three months ended
March 31, 1998, primarily as a result of the reduction of the valuation
allowance.

DISCONTINUED OPERATIONS

         In the third quarter of 1998, the Board of Director's approved the
discontinuance of Trusted Link Procurement ("TLP") business. The $217,000 loss
from discontinued operations is the result of reclassifying the net operating
results of TLP for the three months ended March 31, 1998. (See Note 5 to the
accompanying unaudited consolidated financial statements.)

NET INCOME (LOSS) AND EARNINGS (LOSS) PER SHARE

         Net income applicable to common shareholders increased to $2.3 million
or $0.06 per share for the quarter ended March 31, 1999 from a loss of $1.3
million or ($0.03) per share for the quarter ended March 31, 1998. Net income,
adjusted to exclude a specific $750,000 credit to general and administrative
expense in the first quarter of 1999 and $8.0 million in Charges in the first
quarter of 1998, net of the effect of income taxes at 39%, would have been $1.0
million or $0.3 per share for the first quarter of 1999, compared to $4.4
million or $0.10 per share in the same period in 1998, representing a 76%
decrease in net income from 1998 to 1999.

LIQUIDITY AND CAPITAL RESOURCES

         The Company's working capital decreased $14.8 million to $64.5 million
as of March 31, 1999 from $79.3 million as of December 31, 1998. In the three
months ended March 31, 1999, cash provided by operating activities was $454,000
compared to $1.1 million for the three months ended March 31, 1998. The Company
used net cash in investing activities of $3.9 million for the three months ended
March 31, 1999 compared to $2.4 million for the three months ended March 31,
1998. The change in cash used in investing activities for the period ended March
31, 1999 compared to 1998 was primarily from increased net purchases of
short-term investments. Cash used in financing activities of $15.3 million for
the period ended March 31, 1999 was primarily for the repurchase of common
stock. Cash provided by financing activities for the period ended March 31, 1998
was from the exercise of stock options and warrants and issuance of stock under
the employee stock purchase plan.


                                       2
<PAGE>   13

         Management expects the Company will continue to be able to fund its
operations, investment needs and capital expenditures through cash flows
generated from operations, cash on hand, borrowings under the Company's
uncommitted credit facility and additional equity and debt capital. Several
factors could have an impact on the Company's ongoing cash flows in the future,
including the effects of the Company's ongoing common stock repurchase program,
liquidation of liabilities incurred due to Charges and discontinued operations
and anticipated outlays for the Company's ongoing effort to enhance and
consolidate its information technology infrastructure. The Company does not
believe that inflation has had a material impact on its business. However, there
can be no assurance that Harbinger's business will not be affected by inflation
in the future.

YEAR 2000 COMPLIANCE

         Many currently installed computer systems and software products will
not properly process date information in the time period leading up to,
including and following the year 2000. These systems and products often store
and process the year field of date information as two digit numbers, and
misinterpret dates in the year 2000 and beyond as being dates in the year 1900
or subsequent years. This "Year 2000" issue impacts Harbinger both with respect
to its customers as a developer and vendor of computer software products and
services and internally for its information technology ("IT") and non-IT
systems.

         The Company formed a Year 2000 Steering Committee in July 1998 to
formally address the Company's Year 2000 issues, which formalized the Company's
Year 2000 assessment program begun in March 1997. The Year 2000 Steering
Committee has overseen the Company's Year 2000 Readiness Assessment Program,
which includes establishing the Company's standard for Year 2000 Readiness,
designing test parameters for its products, IT and non-IT systems, overseeing
the Company's remediation program, including establishing priorities for
remediation and allocating available resources, overseeing the communication of
the status of the Company's efforts to its customers, and establishing
contingency plans in the event the Company experiences Year 2000 disruptions.

         The Company describes its products and services as "Year 2000 Ready"
when they have been successfully tested using the procedure proscribed in its
Readiness Assessment Program. This procedure defines the criteria used to design
tests that seek to determine the Year 2000 readiness of a product. Under the
Company's criteria, a software product is Year 2000 Ready if it:

1.       Correctly handles date information before, during, and after January 1,
         2000, accepting date input, providing date output and performing
         calculation on dates or portions of dates.

2.       Functions accurately and without interruption before, during and after
         January 1, 2000 without changes in operation associated with the advent
         of the new century assuming correct configuration.

3.       Where appropriate, responds to two-digit date input in a way that
         resolves the ambiguity as to century in a disclosed, defined and
         pre-determined manner.

4.       Stores and provides output of date information in ways that are
         unambiguous as to century.

5.       Manages the leap year occurring in the year 2000, following the
         quad-centennial rule.

         As of March 31, 1999 Company management estimates that approximately
95% of its product readiness testing has been completed. While most of the
Company's products are presently Year 2000 Ready, the Company currently
estimates that all of its continuing products will be available to customers in
a Year 2000 Ready version by the end of the first quarter of 1999. Certain of
the Company's customers are currently using legacy versions of the Company's
products for which a Year 2000 Ready version will not be developed. The Company
has developed migration plans to move such customers to functionally similar
Year 2000 Ready products. The Company is also in the process of implementing a
website on the Internet that will include a general overview of the Company's
Readiness Assessment Program, including a list of products and the applicable
Year 2000 Ready version numbers of such products.

         The Company is presently engaged in a significant upgrade of
substantially all of its core IT systems, including those related to sales,
customer service, human resources, finance, accounting and other enterprise
resource planning functions, as a result of its growth in recent years. The
Company believes that the upgraded systems, which it expects to have
substantially implemented by mid-year 1999, are all Year 2000 Ready. The Company
is reviewing its remaining IT systems for Year 2000 Readiness, and expects to
modify, replace or discontinue the use of non-compliant systems before the end
of 1999. In addition, the Company is in the process of evaluating its Year 2000
readiness with respect to non-IT systems, including systems embedded in the
Company's communications and office facilities. In many cases these facilities
have been recently upgraded or are scheduled to be upgraded before year-end 1999
as a result of the Company's growth in recent years. The Company is in the
process of distributing surveys to its principal IT and non-IT systems and
services vendors soliciting information on their Year 2000 Readiness as part of
this review. The Company is also surveying its vendors' websites for additional
related information.

         The majority of the work performed for the Company's Year 2000
Readiness Assessment Program has been completed by the Company's staff.
Additionally, the Company engaged outside advisors to evaluate the Readiness
Assessment Program and to participate in certain elements of product testing.
The total costs for completing the Year 2000 Readiness Assessment Program,
including modifications to the Company's software products, is estimated to be
between $1 million and $2 million, funded through the Company's internal
operating cash flows. This cost does not include the cost for new software, or
for modifications to existing software, for the Company's core IT and non-IT
systems, as these projects were not accelerated due to the Year 2000 issue.
Approximately $100,000 to $200,000 in cost remains to be incurred to complete
the Company's Readiness Assessment Program.

         The Company believes that the purchasing patterns of customers and
potential customers may be affected by Year 2000 issues in a variety of ways.
Many companies are expending significant resources to correct or patch their
current software systems for Year 2000 compliance. These expenditures may result
in reduced funds available to purchase software products such as those offered
by the Company. Potential customers may also choose to defer purchasing Year
2000 compliant products until they believe it is absolutely necessary, thus
resulting in potentially stalled market sales within the industry. Conversely,
Year 2000 issues may cause other companies to accelerate purchases, thereby
causing an increase in short-term demand and a consequent decrease in long-term
demand for software products. In addition, Year 2000 issues could cause a
significant number of companies, including current Company customers, to
reevaluate their current software needs, and as a result switch to other systems
or suppliers. Any of the foregoing could result in a material adverse effect on
the Company's business, operating results and financial condition.

         At present the Company has only preliminarily discussed contingency
plans in the event that Year 2000 non-compliance issues materialize. The Company
expects to formalize its contingency plans prior to year-end 1999. In the case
of certain of the Company's value-added network operations, it will be difficult
for the Company to seamlessly implement alternative service arrangements due to
the nature and complexity of the customer interface. While the Company believes
that its Readiness Assessment Program is addressing the risks specific to the
Company for the Year 2000 issue, including its operations in markets outside of
the United States, it cannot be assured that events will not occur that could
have a material adverse impact on its business, operating results and financial
condition. Such events include the risk of lawsuits from customers and the
inability to process data internally on its IT systems. Further, the Company is
aware of the risk that domestic and international third parties, including
vendors and customers of the Company, will not adequately address the Year 2000
problem and the resultant potential adverse impact on the Company. Regardless of
whether the Company's products are Year 2000 compliant, there can be no
assurance that customers will not assert Year 2000 related claims against the
Company.

FORWARD LOOKING STATEMENTS

         Other than historical information contained herein, certain statements
included in this report may constitute "forward looking" statements within the
meaning of the Securities Act of 1933 and the Securities Exchange Act of 1934
related to the Company that involve risks and uncertainties including, but not
limited to, fluctuation of operating results, the ability to compete
successfully, the ability to integrate acquired companies, the impact of Year
2000 compliance and other risks. For further information about these and other
factors that could affect the Company's future results, please see Exhibit 99.1
to the Company's most recent Form 10-K for the year ended December 31, 1998
filed with the Securities and Exchange Commission. Investors are cautioned that
any forward looking statements are not guarantees of future performance and
involve risks and uncertainties and that actual results may differ materially
from those contemplated by such forward looking statements. The Company
undertakes no obligation to update or revise forward looking statements to
reflect changed assumptions, the occurrence of unanticipated events or changes
to future operating results.


PART II.  OTHER INFORMATION


ITEM 4.  SUBMISSION OF MATTERS TO A VOTE OF SECURITY HOLDERS

a)   The Annual Meeting of Shareholders (the "Annual Meeting") of Harbinger
     Corporation (the "Company") was held on April 30, 1999. There were present
     at said meeting in person or by proxy, shareholders of the Corporation who
     were the holders of 33,123,733 shares or 82.0% of the Common Stock entitled
     to vote.

b)   The following directors were elected to hold office for a term as
     designated below or until their successors are elected and qualified, with
     the vote for each director being reflected below:



<PAGE>   14


<TABLE>
<CAPTION>

                                                                  VOTES FOR   VOTES WITHHELD
     Elected to hold office until the 2002 Annual Meeting:

     <S>                                                         <C>              <C>
                  C. Tycho Howle                                 33,029,801       93,932
                  William D. Savoy                               33,026,554       97,179
                  John D. Lowenberg                              33,024,819       98,914
                  Benn R. Konsynski                              33,024,819       98,914
</TABLE>

     The affirmative vote of the holders of a plurality of the outstanding
     shares of Common Stock represented at the Annual Meeting was required to
     elect each director.

     The Directors of the Company continuing in office until the 2001 Annual
     Meeting are as follows: David T. Leach, Ad Nederlof, and David Hildes.
     The directors of the Company continuing in office until the 2000 Annual
     Meeting are as follows: Klaus Neugebauer, Stuart L. Bell, William B.
     King, and James M. Travers.

c)   The proposal to amend the Company's 1996 Stock Option Plan was approved
     with 30,530,592 affirmative votes, 2,422,284 negative votes cast and
     170,857 abstentions. An affirmative vote of the holders of a majority of
     the outstanding shares of Common Stock represented at the annual meeting
     was required to approve the amendment.

d)   The appointment of KPMG LLP as independent public accountants to audit the
     accounts of the Company and its subsidiaries for the year ending December
     31, 1999, was ratified with the votes as follows: 33,049,741 affirmative
     votes, 45,059 negative votes cast and 28,933 abstentions. An affirmative
     vote of the holders of a majority of the outstanding shares of Common Stock
     represented at the annual meeting was required to ratify the appointment of
     KPMG LLP.


ITEM 6.  EXHIBITS AND REPORTS ON FORM 8-K
<TABLE>
<CAPTION>

         <S>                       <C>
         (a)      Exhibits

                  Exhibit 10.1      Fourth Amendment to the Harbinger Corporation Stock Option Plan
                  Exhibit 10.2      Employment Agreement with Douglas L. Roberts
                  Exhibit 11.1      Computation of Earnings per Share
                  Exhibit 27.1      Financial Data Schedule
                  Exhibit 27.2      Restated Financial Data Schedule

         (b)      Reports on Form 8-K

                  Form 8-K dated April 2, 1999 reporting under Item 5 and Item 7 (c) the text of a press release dated
                  March 22, 1999 concerning the Board of Directors approving the purchase of an additional (10%) of
                  the Company's outstanding common shares under its existing stock repurchase program.

</TABLE>


<PAGE>   15






                               S I G N A T U R E S


Pursuant to the requirements of the Securities Exchange Act of 1934, the
registrant has duly caused this report to be signed on its behalf by the
undersigned thereunto duly authorized.


<TABLE>
<CAPTION>

                                                              HARBINGER CORPORATION




<S>                                                           <C>
Date: May 17, 1999                                            /s/ C. Tycho Howle
      -----------------------------------------------         -----------------------------------
                                                              C. Tycho Howle
                                                              Chief Executive Officer
                                                              (Principal Executive Officer)



Date: May 17, 1999                                            /s/ James K. McCormick
      -----------------------------------------------         -----------------------------------
                                                              James K. McCormick
                                                              Chief Financial Officer
                                                              (Principal Financial Officer;
                                                              Principal Accounting Officer)

</TABLE>