Create registry.intra.dominic-ricottone.com/opendkim:latest

Conf in /etc/opendkim/opendkim.conf.

Configuration like

Domain example.com
Selector myselector

KeyFile /path/to/keys/server1.private
UserID opendkim
Socket inet:8891@localhost

Mode s
Canonicalization relaxed/simple

Postfix needs to be configured like:

smtpd_milters = inet:localhost:8891
non_smtpd_milters = $smtpd_milters
milter_default_action = accept

Keypair would be generated like:

opendkim-genkey -r -s myselector -d example.com

The DKIM record should be like:

myselector._domainkey.example.com "v=DKIM1; k=rsa; p=...................."

A common selector is default.

If using syslog, add:

Syslog Yes
SyslogSuccess Yes
LogWhy Yes

I don't think that logging to stdout is an option.