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Q241892: XFOR: NDR with Error 501 Syntactically Invalid HELO Argument(s)

Article: Q241892
Product(s): Microsoft Exchange
Version(s): winnt:5.0,5.5
Operating System(s): 
Keyword(s): exc5 exc55
Last Modified: 06-AUG-2002

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The information in this article applies to:

- Microsoft Exchange Server, versions 5.0, 5.5 
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SYMPTOMS
========

When sending e-mail to a third-party SMTP server or through a firewall, a
non-delivery report (NDR) similar to the following may be generated:

  Subject: Notification: Outbound Mail Failure - A protocol error occurred.

  A mail message was not sent due to a protocol error.

  501 syntactically invalid HELO argument(s)

  The message that caused this notification was:

CAUSE
=====

This error is generated by a third-party SMTP server or firewall.

When the Microsoft Exchange Internet Mail Service establishes a connection to a
remote host, the Internet Mail Service initiates the SMTP conversation with
"EHLO <domainname.com>". If an error is returned, the Internet Mail
Service falls back to "HELO <domainname.com>". If the HELO command returns
an error, an NDR is generated containing the error.

Additional query words:

======================================================================
Keywords          : exc5 exc55 
Technology        : kbExchangeSearch kbExchange500 kbExchange550 kbZNotKeyword2
Version           : winnt:5.0,5.5
Issue type        : kbprb

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