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Exchange server Rejects mails with 451 4.3.0

SarvaDLG
SarvaDLG used Ask the Experts™
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Since last week some known spam messges (email broadcasting my our partners) are getting rejected by our Exchange 2003  server. Our mails are scanned by Postini and we have flagged this doain as safe sender and Junk mail boxes are empty. We think Its our server that rejects the mail. Inteligent messeage filtering is disabled on the server. Need all the help I can get as we don't know if we are loosing other mails as well.
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Barry GillChief of Staff

Commented:
can you post a copy of the DSN (delivery status notification) as a 4.3.0 error is a transient error not commonly used by Microsoft.

Author

Commented:
The sender get the follwing message in their logs

451 4.3.0 Failed in remote data - psmtp [DEFERRED]

Barry GillChief of Staff

Commented:
ok, if that is in the remote senders logs, then that is something happeneing with thier connection to postini.

If they are receiving a bounce message FROM YOUR EXCHANGE server that would be different.

What this appears to be is that the connection back from Postini to you is not reliable. (using this posting as a reference: http://www.phwinfo.com/forum/comp-mail-sendmail/230272-problems-sending-psmtp-postini.html)

Have there been any routing changes on your side recently?
Barry GillChief of Staff

Commented:
as an aside - I work for Mimecast and the security stack we provide gives you full and detailed view into what is happening with your connections. real time queue management, real time logs and lists and full control. Also provide 24/7 telephonic support if you have a real issue you need sorting quickly. Another thing we do is email archiving, so you will never see a time where you are not sure if your messages are being lost or not.

Author

Commented:
I have managed to solve this by disabling ESMTP inspection on ASA firewall. My Firewall version was 7.2 and I was told cisco has resolved the issue in their 8 version. Not sure how it will affect the email security.
Chief of Staff
Commented:
As per what I sent the SAS rule was causing trouble between Postini and yourselves.
I think an assist would at least be worthy?

Author

Commented:
He pointed us in the right direction. Rather than looking at Exchange concentrate more on connectivity