Hi all,
just realized that with a new client installation on latest UCS Forwarding archived mails from the webinterface does not work.
So I digged deeper: first I set the relay:
ucr set mail/relayhost=xx.y.0.112:26
And yes it’s port 26, it’s a ProxMox Mail Gateway 
Also Tested via telnet i PMG accept’s mail from the Benno Docker CT.
Next I tried to take a look into the mail.log, but all mail.* log are emtpy, so I set -v in master.cf for smtpd and restarted postfix. But the log’s remain empty…
If I pass a mail through telnet on localhost I see the following issue in mailq:
root@benno-69061702:/# mailq
-Queue ID- --Size-- ----Arrival Time---- -Sender/Recipient-------
5014418451C 220 Mon Sep 30 10:27:59 benno@client.dom
(client TLS configuration problem)
my@email.dom
-- 0 Kbytes in 1 Request.
And the mail remains in the queue, during my search I ran " postsuper -d ALL" once and removed nearly a dozen Mails from the queue, all from benno users trying to forward mails to themselves!
As there are no log’s I don’t know how to continue…