I am using Mailcow for a couple of time now without a problem. However, while looking through the Postfix logs, it came to my attention, that mailcow is trying to send a message from email@example.com which gets spam filtered:
NOQUEUE: reject: RCPT from [77.22.xxx.xxx]:35122: 550 5.7.1 Service unavailable; client [77.22.xxx.xxx] blocked using zen.spamhaus.org; firstname.lastname@example.org, to=User@mydomain.com, proto=ESMTP, helo=<mail.mydomain.com>
The mailcow server is running under mail.mydomain.com and is handling mails for @mydomain.com. Even though, the server itself is running from a dynamic IP, I use a relay server from my domain provider to circumvent any trouble with spam filters who block incoming mails from those addresses. Maylcow itself however tries the direct approach and ignores the transport map, thus getting trapped by its own spam filter. I tried to add the domain an address in the spam filter whitelis, but to no avail.
Maybe someone can help here?