> So Amavis is setup as an smtpd_milter as well?
No, Amavis is setup as a content_filter (content_filter =
amavis:[127.0.0.1]:10021)
> Do you see DKIM-related Authentication-Results headers in incoming mails?
Yes, please see below at an example e-mail from gmail:
Authentication-Results: smtp.domain.tld (amavisd-new);
dkim=pass (2048-bit key) header.d=gmail.com
