Wietse Venema:
> luc...@dds.nl:
> > Hello,
> >
> > I am managing a Postfix mail relay service in our internal network. The
> > relay itself is more permissive than the downstream SMTP server. So it
> > is possible, and indeed it regularly happens, that my relay accepts a
> > message which is subsequently bounced by the downstream server. There is
> > no way to inform the original sender what happened to the message after
> > the relay accepted it.
> >
> > Is it possible to delay closing the SMTP connection from the original
> > sender until the response from the downstream server is received, and
> > then respond accordingly in the original connection?
> >
> > I could imagine this would imply some complications in terms of
> > performance, and the question what happens if downstream is not
> > available. But in the way it would appear the advantage of telling the
> > original sender what happened to a message, outweighs the disadvantages.
>
> http://www.postfix.org/postconf.5.html#reject_unverified_recipient
If the probkem is that the downstream system rejects email *content*
then you could configure the downstream system as an smtpd_proxy_filter:
1.2.3.4:smtp .. .. .. .. .. .. smtpd
-o smtpd_proxy_filter=downstream.example:25
-o smtpd_proxy_options=
This will accept mail on IP address 1.2.3.4 port 25, and proxy it
to downstream.example port 25.
This requires a different IP address to receive other email.
Wietse
