I have been tracking down a problem with our Exchange 2007 Server for a few hours and finally managed to fix it. Users reported this morning that external emails were not going out, initially I thought this must have been on the Mailsweeper box but after a lengthy investigation it turned out it wasn’t.

I ran the various tests in the toolbox for Exchange 2007 and everything reported in order. No queues were backed up on the Exchange 2007 Server box which led to much scratching of head especially as users were not receiving any messages nor were there any event logs regarding the matter.

I looked at the Send Connector on the Exchange 2007 box that sends all outgoing mail to the Mailsweeper box. I tried disabling it and re-enabling it and it gave me a strange error message. Aha, it was a curious message:

Delivery has failed to these recipients or distribution lists:

’someone@somewhere.com’
Your message wasn’t delivered because of security policies. Microsoft Exchange will not try to redeliver this message for you. Please provide the following diagnostic text to your system administrator.

The following organization rejected your message: ourdomain.com.

  _____  

Sent by Microsoft Exchange Server 2007

Diagnostic information for administrators:

Generating server: mailserver.ourdomain.com

#501 5.7.1 This system is not configured to relay mail (r) from <user@ourdomain.com> to <someone@somewhere.com> for x.x.x.x ##

I deleted the offending send connector and re-created it and the problem went away. Something to keep an eye on possibly…