Christian Vieser:
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> Hi,
>
> we have a two ISP setup and each ISP provides us with an mail relay
> accessible within their networks.
> So we have in our postfix configurations
> relayhost = [relaying.ISP1.com]
> smtp_fallback_relay = [relaying.ISP2.com]
> to provide some fault tolerance. This works pretty good in case we have
> problems with one of our ISPs.
>
> Yesterday ISP1 changed the IP address of his relay. Therefore the
> routing rules on the firewall didn't match any more and the packets went
> down the wrong way. Consequently they were rejected by the relay:
>
> Nov 9 08:56:03 mailhost postfix/pickup[14967]: 4D0373A2C7: uid=104
> from=<XY>
> Nov 9 08:56:03 mailhost postfix/cleanup[15247]: 4D0373A2C7:
> message-id=<20111109075603.4D0373A2C7@mailhost>
> Nov 9 08:56:03 mailhost postfix/qmgr[1496]: 4D0373A2C7:
> from=<[email protected]>, size=1072, nrcpt=1 (queue active)
> Nov 9 08:56:03 mailhost postfix/smtp[15249]: 4D0373A2C7:
> to=<[email protected]>, orig_to=<XYZ>,
> relay=relaying.ISP1.com[aa.bbb.ccc.ddd]:25, delay=0.14,
> delays=0.03/0.01/0.07/0.03, dsn=5.7.1, status=bounced (host
> relaying.ISP1.com[aa.bbb.ccc.ddd] said: 554 5.7.1 <[email protected]>:
> Relay access denied (in reply to RCPT TO command))
> Nov 9 08:56:03 mailhost postfix/bounce[15250]: 4D0373A2C7: sender
> non-delivery notification: 70A193A2C8
> Nov 9 08:56:03 mailhost postfix/qmgr[1496]: 4D0373A2C7: removed
>
> So, first question is: why doesn't postfix try to deliver the mails
> through the fallback relay?
Postfix does not use the fallback relay after a 5XX server reply.
5XX in reply to RCPT TO indicates a permanent error.
> Second question: Even if I had no fallback relay defined, I wouldn't
> like the mails to be discarded as happened here. Is there a way I can
Mail is not discarded. It is returned to the sender address.
Wietse
> instruct postfix to keep the mails in his queue (at least to
> maximal_queue_lifetime ), so that they can be delivered when the problem
> is solved?
>
> Postfix is running under Debian with default values, except the settings
> of relayhost and smtp_fallback_relay.
>
> Thank you for any advice,
>
> Christian
>
