Microsoft KB Archive/105130

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SMTP: Err Msg: WARNING Incoming SMTP Mail From Unknown Host

Article ID: 105130

Article Last Modified on 10/30/2006


  • Microsoft Mail Gateway to SMTP 2.1
  • Microsoft Mail Gateway to SMTP 3.0

This article was previously published under Q105130


Versions 2.1 and 3.0 of Microsoft Mail Gateway to SMTP may display the following message in the SMTPGATE.LOG file, and/or the Gateway PC screen:

[rx] HELO

Note: Using the undocumented switch -CD with the SMTP gateway provides debug information on the gateway screen and log file when full logging is turned on with -GACSY and -LACSY command line options.


This warning indicates that section 3.5 of RFC 821 (the "HELO" command is used to identify the sending host) has been violated. The correct syntax should be:

[rx] HELO hostname.domain


No action is required. The SMTP Gateway will continue to process mail. The message is merely for your information.

For more information refer to RFC 821.

Additional query words: 2.10 3.00 smtp warning helo

Keywords: KB105130