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                                                                    EXHIBIT 99.2

                                                                         [PROXY]

                                MUSTANG.COM, INC.
                               6200 Lake Ming Road
                          Bakersfield, California 93306

           THIS PROXY IS SOLICITED ON BEHALF OF THE BOARD OF DIRECTORS

        The undersigned hereby appoints James A. Harrer and Donald M. Leonard,
and each of them, each with the power to appoint his substitute, and hereby
authorizes each of them to represent and vote as designated below, all the
shares of Common Stock of Mustang.com, Inc. held of record by the undersigned on
April 10, 2000, at the Special Meeting of Shareholders to be held on May 11,
2000 or any adjournments thereof.

                                1.      To approve and adopt the Agreement and
                                        Plan of Merger dated as of February 25,
                                        2000 between Mustang.com and Quintus
                                        Corporation, pursuant to which
                                        Mustang.com will be merged with a
                                        subsidiary of Quintus and each
                                        shareholder of Mustang.com will receive
                                        0.793 of a share of Quintus common stock
                                        for each share of Mustang.com common
                                        stock that shareholder owns.

                                        FOR  [ ]    AGAINST  [ ]    ABSTAIN  [ ]


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                                2.      In their discretion, the Proxies are
                                        each authorized to vote upon such other
                                        business as may properly come before the
                                        meeting.

        This Proxy, when properly executed, will be voted in the manner directed
herein by the undersigned shareholder. If no direction is made, this Proxy will
be voted FOR Proposal 1.

                                        Dated: ______________________, 2000

                                        ____________________________________
                                                   (Signature)
                                        ____________________________________
                                            (Signature if held jointly)

                                        Please sign exactly as name appears
                                        below. When shares are held by joint
                                        tenants, both should sign. When signing
                                        as an attorney, as executor,
                                        administrator, trustee or guardian,
                                        please give full title to such. If a
                                        corporation, please sign in full
                                        corporate name, by President or other
                                        authorized officer. If a partnership,
                                        please sign in partnership name by
                                        authorized person.