We have an SBS 2003 R2 system running, and recently changed (static) IPs as well as ISP.
Since then, every day we get a few messages bounce back. It's completely random, one minute we can send and receive messages to someone, the next we can't.
I am unable to see any warnings or problems in the Message Tracking in Exchange, or the Event Viewer.
I have inserted the message at the end of this question, with substitutions for my server/username.
Thanks in advance :)
From: System Administrator
Sent: 29 November 2010 14:28
To: ONE OF MY USERS
Subject: Undeliverable: RE: XXXXXX
Your message did not reach some or all of the intended recipients.
Subject: RE: XXXXXX
Sent: 29/11/2010 14:24
The following recipient(s) cannot be reached:
RECIPIENT'S NAME on 29/11/2010 14:28
There was a SMTP communication problem with the recipient's email server. Please contact your system administrator.
<MYDOMAIN #5.5.0 smtp;550 <RECIPIENT'S E-MAIL>: Relay access denied>