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dlublink 10-10-2006 10:37 AM

helo fqdn restriction

I have a postfix server that rejects email using 'reject_non_fqdn_hostname' to block messages.

It has now happened three times in the past 2 weeks that a badly configured Microsoft Exchange server has been unable to deliver messages to my server because it is badly configured.

When my server rejects using the above mentioned message (450) I would also like it to automatically generate a message and send it to postmaster@[sending domain] and a second message to the original sending user reminding her that her message will never be delivered until her network adminstrator fixes the problem.

How might I go about doing this?



WindowBreaker 10-13-2006 09:26 PM

Your intentions are honorable. That said, I would NEVER EVER EVER do that. The reason is that you will end up putting yourself on spam blacklists and unable to send mail, since you'll be rejected due to your presence on these blacklists.

For example, lets say I am a spammer. I try to send a bogus message thru your server, send 'helo bla', and give you a sender address of "". You reject my message because of a non-fqdn hostname. But, you also send "" and poor old "" a notification. To them you appear to be spamming, since they never ever sent you an email to begin with.

This will end up happing hundreds of times a day, with you sending out hundreds of notifications to innocent users. Sure a couple of them are misconfigured exchange server, but the rest are not.

My advise is to leave it as is. When a legitimate user tries sending an email that gets rejected, you'll hear about it from your user(s) - believe me. Then you can school the MS Exchange admin on how to properly setup his exchange server. Chances are he's being rejected by other SMTP servers, and you're doing him a favor by enlightening him.


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