If you’re using Postfix for submission and attempts to submit give this messages on the Postix server:
Recipient address rejected: Domain not found
you’re probably chroot’d.
That is, your submssion entry in master.cf looks like this:
submission inet n - - - - smtpd
When it should look like this:
submission inet n - n - - smtpd
Penalty against http://wiki2.dovecot.org/HowTo/PostfixAndDovecotSASL which was my starting point.
My thanks to rob0 and lunaphyte for solving this one.