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Microsoft KB Archive/100352

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Knowledge Base

SMTP: 550 Huh? Extended HELO (EHLO) Not Supported

Article ID: 100352

Article Last Modified on 10/30/2006


  • Microsoft Mail Gateway to SMTP 3.0

This article was previously published under Q100352


Version 3.0 of Microsoft Mail Gateway to SMTP does not accept the extended hello greeting (EHLO). If a host contacts the SMTP gateway computer with "EHLO" instead of "HELO," the gateway replies with a "550 Huh?" and promptly closes the connection so the host can't send the standard "HELO."


Microsoft has confirmed this to be problem in version 3.0 of Microsoft Mail Gateway to SMTP. This problem was corrected in version 3.0.2 of SMTPGATE.EXE. If you do not have version 3.0.2 (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) ftp Change to the Softlib/Mslfiles folder. Get SMTPGW.EXE
  • The Microsoft Network On the Edit menu, click Go To, and then click Other Location. Type "mssupport" (without the quotation marks). 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 errmsg ehlo rfc 821 1425

Keywords: KB100352