This is a bit embarassing, but I'm stuck at the first step of debugging a postfix+dovecot setup on Debian after following this guide.
Sending email from my server works, but receiving doesn't. I get this line in the /var/log/mail.log (with some redactions):
# /var/log/mail.log Oct 18 19:17:03 X postfix/lmtp: BB7321F440: to=<A@X.Y>, relay=X.Y[private/dovecot-lmtp], delay=1157, delays=1095/0.02/0.01/62, dsn=4.3.0, status=deferred (host X.Y[private/dovecot-lmtp] said: 451 4.3.0 <A@X.Y> Internal error occurred. Refer to server log for more information. (in reply to RCPT TO command))
For convenience and emphasis, the key part is:
Internal error occurred. Refer to server log for more information.
The exact same error message appears in /var/log/syslog but there is no additional information there.
Where can I find the "server log" this refers to, so I can continue debugging?