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Some emails sent from our SMTP Server (Windows 2008 running IIS6 SMTP) have begun failing with some of the following errors:

Action: failed Status: 5.5.2 Diagnostic-Code: smtp;504 5.5.2 <178867-WWW1>: Helo command rejected: need fully-qualified hostname

Action: failed Status: 5.5.0 Diagnostic-Code: smtp;550 Access denied - Invalid HELO name (See RFC2821

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Why don't you mark your question as answered? – gWaldo Sep 7 '10 at 17:35
up vote 2 down vote accepted

I'm asking and answering in case others run into this issue...

It turns out that after we installed SP2 for Windows 2008, the FQDN set up in the SMTP settings gets reset to the server name rather than the fully qualified domain name that we had set up originally.

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