Dovecot docker auto-responder - delegate to external SMTP

[Thomas Pronold]

Hi all,

I have dockerized my dovecot setup. Everything works fine besides 
auto-responder using sieve.

Issue is that the my dovecot docker image does NOT come with a SMTP 
which could be used for outgoing mail.

My SMTP setup (postfix) is in another image/container.

I want to keep it that way, so that dovecot and postfix have separate 
images.

So basically I have 2 containers running in the same internal network: 
a) dovecot IP 192.168.10.11 b) postfix IP 192.168.10.22

How do I have to configure dovecot so that it delegates all outgoing 
(autoresponder) mails to the SMTP on IP 192.168.10.22.

The postfix image is configured in a way that certain IPs are allowed to 
send mails without authentication. So on postfix side I am set.

Currently I did a quickfix: I added postfix to dovecot image and 
configured postfix to use the relayhost 192.168.10.22 for mailing. This 
works, still I would prefer having the dovecot image not containing an 
postfix SMTP.

Thanks

Tom