Employment Agreement - IDT Corp. and Clifford M. Sobel
                            [NET2PHONE LETTERHEAD]
                                 May 12, 1999
Clifford M. Sobel
40 Dorrison Drive
Short Hills, New Jersey  07078
Dear Cliff:
     This letter is being entered into in connection with the amendment among
Net2Phone, Inc. ("Net2Phone"), IDT Corporation ("IDT") and you, dated May 11,
1999 (the "Amendment"), to the original employment agreement between you and
IDT, dated May 1, 1997 (the "Agreement"). While the Amendment made Net2Phone a
party to the Agreement, we have asked for you and IDT to execute this letter
agreement to clarify two points with respect to the Amendment and the Agreement.
     1.   It is the intention and desire of the parties to amend Section 8 and
          Section 12 of the Agreement to include Net2Phone within the purview of
          the nondisclosure and non-compete provisions contained therein.
          Therefore, Section 8 and Section 12 of the Agreement are hereby
          amended to include Net2Phone along with the Company (as defined in the
          Agreement) for purposes of your nondisclosure and non-compete
          obligations as set forth in Section 8 and Section 12 of the Agreement.
     2.   This letter shall also clarify that you executed the Amendment in your
          capacity as an individual and not as an officer of Net2Phone.
     Please acknowledge your acceptance to the terms of this letter by executing
below.
                                        Very truly yours,
                                        Howard S. Balter
                                        Chief Executive Officer
AGREED TO AND ACCEPTED:
                                              IDT CORPORATION
/s/ Clifford M. Sobel                        By: /s/ Joyce Mason
--------------------------------                ------------------------------
Clifford M. Sobel                               Name: Joyce Mason
                                                Title: General Counsel