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From: Wietse Venema (wietseporcupine.org)
Date: Wed Nov 18 2009 - 10:35:02 CST
> Thanks Andreas,
> The reject would be '553 Mail from ... not allowed', so it sounds like
> a dead end trying to configure postfix to handle this.
> Suggestions on how to workaround are welcome.
This is essentially the same problem as home office sites trying
to send direct mail from a residential pool with fall-back to some
ISP because their address is listed in zen.spamhaus.org.
smtp unix - - n - - smtp
When the direct-to-destination delivery attempt fails, it will be
the same Postfix SMTP client process that dumps the message to the
fallback host, so 5xx replies will be ignored in both cases, and
mail may remain queued forever.
Ignoring 5xx responses is not kosher use of SMTP, and there is no
enthousiastic support for Postfix to give 5xx replies a treatment
that depends on context.
> ~ Remus
> On Nov 18, 2009, at 1:12 AM, lst_hoe02kwsoft.de wrote:
> > Zitat von "contactrusanu.com" <contactrusanu.com>:
> >> Is there a way to configure postfix to use a relay only if direct
> >> delivery is rejected? The case being a web application that has to
> >> send notification to subscribers, but some servers reject the
> >> connection (app IP originates from AWS EC2). I want those cases to
> >> be retried using a paid SMTP relay like authsmtp.com. However I
> >> don't want to use the relay for everything since it costs per mail.
> > If it is rejected with a permanent error code (5xx) no retry an no
> > fallback will happen. This is required by RFC.
> > If the reject is with some temporary reject code or the connection
> > is not accepted at all you need the fallback_relay parameter.
> > Regards
> > Andreas