Microsoft KB Archive/108052

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SMTP: Err Msg: Recipient Unknown

Article ID: 108052

Article Last Modified on 10/30/2006


  • Microsoft Mail Gateway to SMTP 3.0

This article was previously published under Q108052


Version 3.0 of Microsoft Mail Gateway to SMTP generates non-delivery notices for non-existent recipients, and reports the following error message:

Recipient unknown


The gateway parses the comment part of an address as additional addresses. When the intended recipient tries to reply to all the addresses saved, some addresses are invalid and do not represent real recipients.


Microsoft has confirmed this to be problem in version 3.0 of Microsoft Mail Gateway to SMTP. This problem was corrected in version 3.0.8 of SMTPGATE.EXE. If you do not have version 3.0.8 (or later), you can obtain the latest version from the Microsoft Software Library (MSL). Download SMTPGW.EXE (S14223), a self-extracting file, from any of the following services:

  • Microsoft's World Wide Web Site on the Internet

On the home page, click the Support icon.
Click Knowledge Base, and select the product.
Enter kbfile SMTPGW.EXE, and click GO!
Open the article, and click the button to download the file.

  • Internet (anonymous FTP)

Change to the Softlib/Mslfiles folder.

  • The Microsoft Network

On the Edit menu, click Go To, and then click Other Location.
Type mssupport.
Double-click the MS Software Library icon.
Find the appropriate product area.
Locate and Download SMTPGW.EXE.

For additional information about downloading, please see the following article in the Microsoft Knowledge Base:

119591 How to Obtain Microsoft Support Files from Online Services

Additional query words: 3.00

Keywords: KB108052