Re;
I think I've find a bug in OpenDKIM plugin: https://github.com/i-MSCP/plug…/backend/OpenDKIM.pm#L853
For me, the statement is wrong there ( should be added in smtpd_milters instead and non_smtpd_milters should reference smtpd_milters.
I'll check the behavior when installing the plugin together (OpenDKIM, SpamAssassin and fix if needed. I'll do this this week-end because I'm already busy with other plugins ( Monitorix, OwnDDNS ...) which must be updated for the 1.2.x serie.