I have Linode VPS web.domain.uk sending daily newsletters through another Linode VPS box.domain.uk. This has worked well for over a year. On 6 Jan I updated box.domain.uk to bionic mailinabox (before 0.40 release). No issue, newsletters went out daily until 13 Jan but have not gone out 14 & 15 Jan. mail.log shows:
NOQUEUE: reject: RCPT from unknown[2a01:7e00:f03c:xxxx;xxxx:xxxx]: 553 5.7.1 email@example.com: Sender address rejected: not owned by user firstname.lastname@example.org; email@example.com firstname.lastname@example.org proto=ESMTP helo=<web.domain.uk>
disconnect from unknown[2a01:7e00:f03c:xxxx;xxxx:xxxx] ehlo=2 starttls=1 auth=1 mail=1 rcpt=0/1 quit=1 commands=6/7
So, what changed on 13 Jan? On that date I updated with
apt-get update && apt-get upgrade
and added several other additional domains to box.domain.uk such as domain.org.uk and domain2.org.uk.
Apart from the inability of server web.domain.uk to log into box.domain.uk with the username email@example.com and the password of that domain everything is working fine and the mailinabox status checks are ok. I can log into firstname.lastname@example.org with Roundcube.
I am at a loss to explain this change of behaviour or fix the problem. Any clue or suggestion would be much appreciated.
[SOLVED] Lesson learned: an alias over-rides a mailbox; when making an alias be sure you don’t have a mailbox with the same name. I had completely wrongly put an alias of email@example.com to firstname.lastname@example.org. Deleting this alias solved the problem.