EXHIBIT 10.23


                                    July ___,  1996



FTP Software, Inc.
100 Brickstone Square, Fifth Floor
Andover, Massachusetts  01810

     Re:  Firefox Communications, Inc.

Ladies and Gentlemen:

     The undersigned understands that FTP Software, Inc., a Massachusetts
corporation ("PARENT"), Firefox Acquisition Corp., a wholly owned subsidiary of
Parent ("MERGER SUB"), and Firefox Communications Inc., a Delaware corporation
(the "COMPANY"), have entered into an Amended and Restated Agreement and Plan of
Merger dated May 21, 1996 (as amended and restated and in effect from time to
time, the "MERGER AGREEMENT"), pursuant to which Merger Sub would be merged (the
"MERGER") with and into the Company, and each outstanding share of common stock,
par value $.001 per share, of the Company ("COMPANY COMMON STOCK") would be
converted into the right to receive (a) that number of shares of common stock,
par value $.01 per share, of Parent ("PARENT COMMON STOCK") that equals the
amount obtained by dividing (i) $50,000,000 divided by the number of shares of
Company Common Stock issued and outstanding immediately prior to the effective
time of the Merger (the "OUTSTANDING FIREFOX SHARES") by (ii) the average
closing price of the Parent Common Stock as quoted on the Nasdaq National Market
for the 10 trading days immediately preceding the date of the Firefox Meeting,
subject to the provisions in the Merger Agreement relating to fractional shares,
and (b) cash in the amount of $10,000,000 divided by the number of Outstanding
Firefox Shares, subject to adjustment as described in the Merger Agreement.
Capitalized terms not otherwise defined herein are used herein as defined in the
Merger Agreement.

     Parent has requested the undersigned to agree, and the undersigned has
agreed, with Parent as follows:

     1.   Certain Transfer Restrictions.

     The undersigned has been advised that the issuance of shares of Parent
Common Stock to the undersigned, if any, pursuant to the Merger will be
registered under the Securities Act

 
of 1933, as amended ("SECURITIES ACT"), pursuant to a registration statement on
Form S-4. The undersigned has also been advised that, if the undersigned is an
"affiliate" of the Company at the time the Merger is submitted to a vote of the
stockholders of the Company, Rule 145 under the Securities Act will restrict the
undersigned's sales of shares of Parent Common Stock, if any, received by the
undersigned in the Merger.  Nothing contained herein shall be construed as an
admission that the undersigned is an "affiliate" of the Company.  The
undersigned has been advised that if the undersigned is so subject to Rule 145,
the undersigned may not sell or otherwise dispose of any such shares of Parent
Common Stock except in accordance with Rule 145(d) under the Securities Act or
pursuant to an effective registration statement under the Securities Act or an
exemption from the registration requirements of the Securities Act.

     The undersigned understands and agrees that:

     (i)   Parent is under no obligation to register the sale, transfer or other
disposition of the shares of Parent Common Stock, if any, to be received by the
undersigned in the Merger except as set forth in written agreements, if any,
with or for the benefit of the undersigned that may have been entered into by
Parent.

     (ii)  Stop transfer instructions will be given to the transfer agent of
Parent with respect to the shares of Parent Common Stock, if any, to be received
by the undersigned in the Merger, and there will be placed on the certificate
representing such stock, or any certificates delivered in substitution therefor,
a legend stating in substance:

     "THE SECURITIES REPRESENTED BY THIS CERTIFICATE WERE ISSUED IN A
     TRANSACTION TO WHICH RULE 145 UNDER THE SECURITIES ACT OF 1933 (THE "ACT")
     APPLIES.  THE SECURITIES REPRESENTED BY THIS CERTIFICATE MAY BE TRANSFERRED
     ONLY IN ACCORDANCE WITH RULE 145(d) OR PURSUANT TO AN EFFECTIVE
     REGISTRATION STATEMENT OR EXEMPTION FROM REGISTRATION UNDER THE ACT."

     (iii)  Unless the transfer by the undersigned of the shares of Parent
Common Stock, if any, to be received by the undersigned in the Merger is a sale
made in conformity with the provisions of Rule 145(d), or is made pursuant to a
registration statement under the Securities Act, Parent reserves the right to
put an appropriate Securities Act legend on the certificate issued to a
transferee.

     In connection with the foregoing, Parent represents and agrees as follows:

     (i)   For so long as and to the extent necessary to permit the undersigned
to sell the shares of Parent Common Stock, or any permitted transferee of any
such shares to

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sell such shares, pursuant to Rule 145 and, to the extent applicable, Rule 144
under the Securities Act, Parent shall use its best efforts to file, on a timely
basis, all reports required to be filed by it with the Securities and Exchange
Commission ("SEC") pursuant to Section 13 of the Securities Exchange Act of
1934, as amended (the "EXCHANGE ACT"), so long as it is subject to such
requirement, shall furnish to the undersigned or any such transferee upon
request a written statement as to whether Parent has complied with such
reporting requirements during the 12 months preceding any proposed sale under
Rule 145 and shall otherwise use its reasonable best efforts to permit such
sales pursuant to Rule 145 and Rule 144.

     (ii)  Parent agrees that the stop transfer instructions and legends
referred to above in this section 1 shall be promptly terminated or removed if
the undersigned or any such transferee shall have delivered to Parent a copy of
a letter from the staff of the SEC or an opinion of counsel with recognized
expertise in securities law matters and reasonably acceptable to Parent, in form
and substance reasonably satisfactory to Parent, to the effect that such
instructions and legends are not required for the purposes of the Securities
Act.

     2.  Miscellaneous.

     This letter agreement shall be governed by and construed in accordance with
the laws of The Commonwealth of Massachusetts.

     Please indicate your agreement with the foregoing by signing the
acknowledgment below on the enclosed copies of this letter, and returning the
same to the undersigned, whereupon this letter agreement shall become an
effective agreement between Parent and the undersigned.

                              Very truly yours,


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

                              By: 
                                  ---------------------------------
                              Name:
                              Title:

Acknowledged and agreed as of
the date hereof:

FTP SOFTWARE, INC.

By
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     Name:
     Title:






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