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Postfix - Do not generate bounce messages in some cases.

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LaGatorVII

IS-IT--Management
Nov 26, 2008
1
US
Ok here is the problem. My postfix server is the front end for 2 exchange servers running Symantec Mail Security with spam filtering. The most important thing is to cut down the spam as much as possible. We go to great pains to maintain a proper list of recipients so we don't have "User Unknown" bounce messages. The problem is that some times mail gets through the postfix filters, but then is rejected by the Exchange servers with the message "550 5.7.1 Requested action not taken: message refused" This will then generate a bounce to an email that, because it was spam in the first place does not have a proper email server. So my deferred queue eventually gets huge.

To help stay on top of this issue, I have been manually making sure that both exchange servers are up and then running 'postsuper -d ALL deferred' on the postfix server to get rid of those bounces the server is constantly trying to send. I have figured out that there are about 25 per day. So if they stay in the queue after one week the server is constantly retrying to send 175 messages in addition to the normal load which is huge.

I see two possible solutions, both of which I am not savvy enough to do on my own:

1) Some setting or filter in Postfix to not generate a bounce message when an email is rejected for the above reason.

2) Some script to delete mail messages via a cron job if they include the above rejection reason. "550 5.7.1 Requested action not taken: message refused". I might be able to figure out a script that can delete the files at the file level but I am not sure what this would do to Postfix.

Please note that the Postfix server is locked down pretty good. All of the helo, sender and recipient restrictions are in place, as well as two RBL filters. It is just that about 25 times per day the Exchange servers are a little better at filtering, and we do not want those extra mails to get through to the users.

Any help is greatly appreciated. Thanks in advance.

Robert White
 
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