Gábor Lénárt wrote:
Hei,
I have a got a stupid problem. We have some customers saying they can't and
don't want to reconfigure their mail servers even if Planet-X hits Earth and
that would help to avoid it :) And their MTAs always responds with:
450 <u...@domain>: Recipient address rejected: User
unknown in local recipient table (in reply to RCPT TO command))
if there is an invalid, non existing mail address there. However they argues
that they would like us not to try to deliver mails again and again. It's
also a problem for us because of many mails waiting in the queue. They want
us to handle this situation somehow.
Is it possible with postfix to parse the response of the remote MTA somehow,
and modify the meaning of the SMTP code (to some 5xx or so) based on the
text after the SMTP error code? I think just looking for "450" is not enough
because there are other responses as well with this error code. I can't find
anything like this in postfix (and to be honest, I can understand that it's
not a normal request) though. Maybe I need another software, like some kind
of SMTP proxy or whatever to do that? Any ideas?
I know it's a really stupid idea (the normal and logical solution would be
to ask them to reply with 5xx not with 4xx in this case), but it's on a
separated network, so there will be no problems on Internet in general, it's
a controlled and closed environment.
thanks in advance,
Sounds as if you are providing mail gateway service for one or
more third parties. OK.
Also sounds as if you don't have a valid recipient list for
these customers. Not OK. Your queue is likely filled with
lots of undeliverable mail to unknown recipients, and
undeliverable bounces to bogus senders, plus you're sending
out backscatter to innocent parties. This will get you
blacklisted.
The solution is two steps.
First, if you can't get a valid recipient list you can use
address verification so that you don't accept mail to bogus
users in the first place. This is really important.
http://www.postfix.org/ADDRESS_VERIFICATION_README.html#recipient
The second step isn't required, but will reduce load on your
system. Convince them (use a creative explanation about
system security) to log in as root and run this one-line patch
to their system:
postconf -e unknown_local_recipient_reject_code=550
--
Noel Jones
