"Deferred" status DSNs

>However, e-mails have gone missing since the 10th of December and I only just found out the hard way last night (13th January), that this has been going on.

I believe security policy errors currently defer delivery instead of failing it with a permanent error (and thus notifying you immediately). With default configuration it means messages get stuck in the queue for up to 5 days before actually giving up even if it is hopeless. The reason for this behavior is potential intermittent nature of various delivery failures. Sorry for your experience.

Do you think implementing a notification saying that the message is not delivered is a good solution to this?

_Originally posted by @foxcpp in https://github.com/foxcpp/maddy/issues/301#issuecomment-760409433_