zacaj's questions

I host my own mail server using postfix/dovecot. Recently, I've gotten a few "email rejected" emails acting like my server sent spam from an account that doesn't exist on my server. I've searched through /var/log/mail.log for any occurrences of that account name, or the receiving server's name, etc, but can't find anything. So the possibilities I can come up with are either:

1. these are fake rejection emails being sent to me for some reason
2. I'm not searching for the right stuff in the logs, or not searching the right logs, etc
3. Somehow my server is sending email without logging it

Is there any way to really confirm which one of these is the case? I don't want my host to get mad at me for unknowingly relaying spam

For reference, I've tried commands like:

cat mail.log |grep -v "relay=local" |grep "relay=" |grep "status=sent"
cat mail.log | grep submission
grep -o 'to=<[^@]@.[^>]' /var/log/mail.log
cat mail.log | grep <HOST URL>
cat mail.log | grep <SENDER USER NAME>

I also added default_transport = error: This server sends mail only locally. to my postfix/main.cf file, which supposedly disables all outbound mail, but still got another 'email rejected' type mail returned the next day

I want to set up a mail server using postfix and dovecot, that stores mail using the maildir format, and I don't want any of these files to go in user's home directories. Wherever I search for how to make postfix use maildir, they just say to set

home_mailbox = Maildir/

but this places mail in the home home directory.

dovecot nicely lets you specify any path, and also gives you %u to customize it, so I set it to

mail_location = maildir:/var/mail/users/%u/:INBOX=/var/mail/users/%u/INBOX

I don't really mind moving the INBOX around, as long as it's not in /home, but I can't find any way to do this. I don't want to bother with virtual users, or procmail, or anything.