On Fri, Jun 20, 2025 at 10:37:53PM +0200, Christian H. Kuhn via Postfix-users
wrote:
> Dear Wietse,
>
> Am 20.06.2025 um 22:26 schrieb Wietse Venema via Postfix-users:
> > Christian H. Kuhn via Postfix-users:
> > I see only one inet_interfaces setting, and two differfent myhostname
> > settings. The Postfix SMTP client detects a mail loop when it
> > wants to connect to port 25 and:
> >
> > - Either the server IP address matches the client's inet_interfaces
> > setting (in this case Postfix does not even attempt to connect).
>
> This is it. But how can it be avoided in a multi instance set up, if all
> instances are running on the same server and use the same localhost? No IP
> but UNIX sockets?
>
> > - Or the server greets the client with the client's myhostname (in
> > this case the client logs that the server greets with its own hostname).
>
> As the cited doc said, i used different hostnames for both port 25
> instances.
Don't include loopback IP addresses in the inet_interfaces list of the
"input" instance, which will accept mail only on the public IP addresses.
Include *only* the loopback IP addresses in the inet_interfaces of the
"output" instance, which will accept mail only on the loopback IP
addresses.
Assign both instances explicit distinct $myhostname values.
--
Viktor.
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