Merge branch 'master' into 'stable-3.1'

cleanup postfix-config

"smtpd_restriction_classes = greylisting" and "greylisting = check_policy_service inet:127.0.0.1:10023" should not be added to main.cf is greylistening is not installed. i think, it's possible to use some more placeholders during configure_postfix


See merge request !315