efa-project.org

if I disable the mailscanner milter in postfix (running efa4 latest), this error goes away:
milter-discard: END-OF-MESSAGE from 50-242-229-149-static.hfc.comcastbusiness.net[50.242.229.149]: milter triggers DISCARD action; from=<denis.hofmann@t-online.de> to=<matt@efs.org> proto=ESMTP helo=<t-online.de>
happens with every inbound email. dkim and dmarc are happy.
Any tips on diagnosing what's happening here?

I think you might be misinterpreting the logs. Have you followed all entries related to that particular email? Are you sure it actually gets discarded? I just quickly glanced at the logs and that message is present on emails that get delivered.

Also, posting such partial entries of the log makes it difficult to look at a problem from a distance. You should probably search the message-id in your log to see all the entries related to that message. Disabling the Milter obviously defeats the purpose.

Regards,
A.