Add options to reject or quarantine emails that fail or have invalid DKIM
Currently, even if an email fails DKIM verification it is delivered. There should be, at the very least, an option to quarantine emails that aren't successfully verified. Also see https://community.sophos.com/products/unified-threat-management/f/mail-protection-smtp-pop3-antispam-and-antivirus/112950/dkim-verification/.
The DKMIM incoming check is necessary, as it doesn't make sense to have DKIM outgoing but not incoming.