Hi,
I’ve tried to use a Mailcow mailbox as destination for Exchange 365 journaling (= basically a copy of all 365 mails is send to the Mailcow mailbox, e.g. journal@example.com). I’ve listed the 365 sender address (admin@365example.com) on the spam filter whitelist.
Sadly this works for some mails only. About 30 % can be seen in rspamd. They are accepted and delivered to the mailbox (MAILCOW_WHITE (-999)).
The other 70% are not even shown in rspamd, the are rejected beforehand. The 365 admin mailbox shows Remote Server returned '550 5.1.0 Recipient rejected: journal@example.com Not sure why some are rejected and others not.
Maybe it is because the “To:” header shows only non Mailcow domains? Is the To: header checked?
I’ve tried some other mail providers as journal destination and no mails are rejected there.
Any ideas?