Erratic Undelivered Mail Issue

Hi guys
I’m a newbie on the forum, so apologies if I’m being naive with anything - but we’ve been having problems receiving emails from some (but not all) of our clients. When they try send us emails, they get the Undelivered Mail message I’ve copied below.

I’ve also tried sending emails to myself from other accounts & I haven’t received anything in reply! No emails delivered & no Undelivered Mail messages!?

Does anyone have any suggestions what may be causing this? And why only some clients are experiencing this problem?


------ Forwarded Message
Subject: Undelivered Mail Returned to Sender

This is the Postfix program at host

I’m sorry to have to inform you that your message could not be be delivered to one or more recipients. It’s attached below.

For further assistance, please send mail to

If you do so, please include this problem report. You can delete your own text from the attached returned message.

The Postfix program

<[Recipients Email]>: host[] said: 250 Accepted (in reply to DATA command)
Reporting-MTA: dns;
X-Postfix-Queue-ID: 0DA808701E
X-Postfix-Sender: rfc822; [Senders Email]
Arrival-Date: Tue, 7 Aug 2007 20:45:04 -0700 (PDT)

Final-Recipient: rfc822; [Recipients Email]
Action: failed
Status: 5.0.0
Diagnostic-Code: X-Postfix; host[] said: 250 Accepted (in reply to DATA command)

------ End of Forwarded Message