Some semi-recent upgrades must have broken my postfix+dovecot configuration, but I'm having problems finding out what the cause is.

My domain is simendsjo.me with the MX record mail.simendsjo.me.

I can send mail to both local and external recipients, and it delivers mail from internal mailboxes.

The problem is that mail from external senders isn't delivered, and nothing is logged at all. The external sender also doesn't receive any errors.

I have no idea where to ever start looking as nothing is logged at all when external mail is sent to my server.

So the first issue would be: How can I turn on some debug messages for postfix?

I've tried:

debug_peer_level = 2
debug_peer_list = simendsjo.me

.. And _level = 999 and _list = gmail.com where I'm trying to send emails from. but nothing is logged.

When sending mails from a local mailbox (but from an outside computer, not localhost), a lot is logged.

I don't have any rules in iptables either.

Any ideas how I can get some debug messages for postfix?