Exhibit (a)(1)(iii)

NOTICE OF GUARANTEED DELIVERY

To Tender Shares of Common Stock

of

NET2PHONE, INC.

Pursuant to the Offer to Purchase, Dated November 10, 2005

by

NTOP ACQUISITION, INC.,

a Wholly-Owned Subsidiary

of

IDT CORPORATION

(Not to be Used for Signature Guarantees)

THE OFFER AND WITHDRAWAL RIGHTS WILL EXPIRE AT 5:00 P.M., NEW YORK CITY TIME, ON MONDAY, DECEMBER 12, 2005, UNLESS EXTENDED.

This Notice of Guaranteed Delivery, or a form substantially equivalent hereto, must be used to accept the Offer (as defined below) (i) if certificates (“Certificates”) evidencing shares of common stock, par value $0.01 per share, of Net2Phone, Inc., a Delaware corporation (the “Shares”), are not immediately available, (ii) if the procedure for delivery by book-entry transfer cannot be completed prior to the Expiration Date (as defined in the Offer to Purchase), or (iii) if time will not permit all required documents to reach the Depositary prior to the Expiration Date. This Notice of Guaranteed Delivery may be delivered by hand, transmitted by facsimile transmission or mailed to the Depositary. See “The Offer — Section 3. Procedures for Tendering Shares” in the Offer to Purchase.

The Depositary for the Offer is:

Wachovia Bank, N.A.

By Hand:	By Mail:	By Overnight Mail or Courier:
Corporate Actions — NC 1153 1525 West W.T. Harris Boulevard, 3C3 Charlotte, NC 28262-8522	Corporate Actions — NC 1153 1525 West W.T. Harris Boulevard, 3C3 Charlotte, NC 28262-8522	Corporate Actions — NC 1153 1525 West W.T. Harris Boulevard, 3C3 Charlotte, NC 28262-8522

By Facsimile Transmission (Eligible Institutions only):

(704) 590-7599

Confirm Receipt of Facsimile by Telephone (Call Toll-Free): (800) 829-8432

Delivery of this Notice of Guaranteed Delivery to an address other than as set forth above, or transmission of instructions via a facsimile transmission other than as set forth above, will not constitute a valid delivery.

This form is not to be used to guarantee signatures. If a signature on a Letter of Transmittal is required to be guaranteed by an “Eligible Institution,” such signature guarantee must appear in the applicable space provided in the signature box on the Letter of Transmittal.

The Eligible Institution that completes this form must communicate the guarantee to the Depositary and must deliver the Letter of Transmittal or an Agent’s Message (as defined in “The Offer — Section 3. Procedures for Tendering Shares” in the Offer to Purchase) and Certificates representing the Shares to the Depositary within the time period specified herein. Failure to do so could result in financial loss to the Eligible Institution.

Ladies and Gentlemen:

The undersigned hereby tenders to NTOP Acquisition, Inc., a Delaware corporation and a wholly-owned subsidiary of IDT Corporation, a Delaware corporation, upon the terms and subject to the conditions set forth in the Offer to Purchase, dated November 10, 2005 (the “Offer to Purchase”), and the related Letter of Transmittal (which, together with the Offer to Purchase, constitute the “Offer”), receipt of each of which is hereby acknowledged, the number of Shares specified below pursuant to the guaranteed delivery procedure described under “The Offer — Section 3. Procedures for Tendering Shares” in the Offer to Purchase.

Number of Shares: 

            Please Type or Print

Share Certificate Number(s) (if available): 

Please check this box is Shares will be tendered by book-entry transfer: ¨

Account Number: 

Date: 

Name of Record Holder(s): 

Address: 

Telephone No.: 

Signature(s): 

Dated: 

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GUARANTEE

(Not to be Used for Signature Guarantees)

The undersigned, a firm that is a member in the Security Transfer Agent’s Medallion Program, the New York Stock Exchange Medallion Program, the Stock Exchange Medallion Program or any other “Eligible Guarantor Institution,” as such term is defined in Rule 17Ad-15 under the Securities Exchange Act of 1934, as amended (each, an “Eligible Institution”), guarantees to deliver to the Depositary, at one of its addresses set forth above, either Certificates evidencing the Shares tendered hereby in proper form for transfer, or confirmation of book-entry transfer of such Shares into the Depositary’s account at the Depository Trust Company, in each case with delivery of a properly completed and duly executed Letter of Transmittal (or facsimile thereof), with any required signature guarantees, or an Agent’s Message (as defined in the Offer to Purchase) in the case of a book-entry transfer, and any other required documents, all within three Nasdaq National Market trading days after the Expiration Date.

Name of Firm: 

Authorized Signature: 

Name: 

            (Please Type or Print)

Title:  

Address: 

Zip Code: 

Telephone No.: 

Dated: 

NOTE: DO NOT SEND SHARES WITH THIS FORM; SHARES SHOULD BE SENT WITH YOUR LETTER OF TRANSMITTAL SO THAT THEY ARE RECEIVED BY THE DEPOSITARY WITHIN THREE NASDAQ NATIONAL MARKET TRADING DAYS AFTER THE DATE OF EXECUTION OF THE NOTICE OF GUARANTEED DELIVERY.

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