> On Apr 14, 2018, at 12:23 AM, Christos Chatzaras <ch...@cretaforce.gr> wrote: > > I think the only way to fix this is to have 2 postfix instances, right? One > for incoming and one for outgoing.
If you want to round-trip mail through an external SMTP server, and then bring it back to the same host, then yes, there typically need to be two queues (Postfix instances), one that sends all mail out, and another that accepts and delivers. One can play games with rewriting, so that mail originally rewrites to a domain that goes off-box, possibly rewrites in the outbound smtp delivery agent smtp_generic_maps, and then returns into an smtpd(8)/cleanup(8) pair that does no or different rewriting. That could make it possible to use a single queue, because the destination domain would be different for returned mail than for originally incoming mail. -- Viktor.