Roel van Meer:
> Victor Duchovni writes:
>
> > This would be wrong. The "ssmtp" service, if it existed, is generally
> > for submission, not inbound MX delivery, and almost always requires
> > authentication, which you will not be able to provide. You would get
> > random rejection of your email if you guess random ports on the peer
> > system to deliver to.
>
> Then let me rephrase my question: is there a way to configure postfix,
> within a single instance, to try delivery on port 25, and to retry delivery
> on another port if that fails? I'm not guessing random ports here, I just
> want delivery to be retried via another way if normal smtp delivery fails.
> It doesn't really matter to me whether that is via smtp on a non-standard
> port or via smtp with TLS/SS.
It does matter.
The submission service (port 587) requires authentication. The
ssmtp service (port 465) requires a protocol that has been deprecated
for years, and that is not even implemented in the Postfix SMTP
client.
So that kills off the STANDARD mail ports.
> > The right answer is to negotiate the right port with each downstream client,
> > and use a transport table.
>
> That is true, yes. I know it can be done this way, but what I am looking
> for is a generic solution that tries delivery on port 25 first, and on port
> n next. The goal is to prevent the requirement of configuring each client
> separately.
That is a mistake.
You can't simply assume that all your customers will accept mail
on some NON-STANDARD port number. This requires prior arrangements,
plus a transport map entry.
Wietse
