Platform: Linux Fedora 27 In a special case Postfix (3.3.0 and 3.2.5 at least) will silently discard emails without logging anything about it.
After moving to a new server a lot of mail was delivered to the luser_relay user, and when changing this user to the main user of the system, all emails were lost with the only trace of them in the maillog as one line of postfix/qmgr: ACA2B201E3B00: removed after received from amavisd. The cause of this is the following: The sequence of users in /etc/passwd had changed. For historical reasons there are some users and groups in /etc/passwd and /etc/groups which have been allocated the same number and this is normally working fine regardless of the sequence in /etc/passwd. e.g. user1:x:1715:1715:User A:/home/user1/./:/sbin/nologin user2:x:1715:1715:User B:/home/user2/./:/sbin/nologin The ls command will use the latest listed user ll /home/user1 -d drwx--x--x. 3 user2 user2 274 2015-06-23 20:08 /home/user1 Apparently Postfix is doing the same when determining the user of the mailbox file. However, Postfix is then considering mail to user1 as not deliverable, because the owner of the mailbox is textually user2 (which is really only an alias for user1). Postfix wil then deliver to the luser_relay user, but if this user is a similar user e.g. user1, the email is silently discarded. I have not tested it without luser_relay. I would prefer Postfix to deliver the emails or let them stay in the mail queue, but if not, at least it should emit an error message in the log when discarding messages. - Jørgen Thomsen