Ok here is a weird one.
I can't find info on this error anywhere I have looked.
Arrival-Date: Fri, 13 Aug 2010 23:00:14 -0400
Reporting-MTA: dns; ecout2
Diagnostic-Code: smtp; 554 5.4.5 [internal] Delivery not attempted (maximum retries)
Final-Recipient: rfc822; firstname.lastname@example.org
Last-Attempt-Date: Fri, 13 Aug 2010 23:00:14 -0400
This message was created automatically by the mail system (ecelerity).
A message that you sent could not be delivered to one or more of its recipients. This is a permanent error. The following address(es) failed:
>>> email@example.com (while not connected): 554 5.4.5 [internal]
not attempted (maximum retries)
The sender claims he can can send attachments to the address, but we have received attachments from him as recent as Friday. He received this message tonight on a NDR