I found this error message in the mail.log and I am curios why this happens.
Apr 8 15:07:59 srv02 dmarc[20617]: Mail delivery from '/opt/psa/handlers/spool/message1JprPL' to '
[email protected]' into 'INBOX.Spam' failed with return code 67
[email protected] is no inbox it is just used to forward...