We can easily send out an echo notification to the recipient actually - we have the $user in $failedUser here in https://github.com/wikimedia/mediawiki-extensions-BounceHandler/blob/master/includes/BounceHandlerActions.php#L68

Discussed with @Jgreen and we found the following issues in implementing this one:

1. In the current approach, we CANNOT get the details of the sender from a bounce email, and we can maybe notify the user - "Hey, an email to you just got bounced".

Something that we thought would work is changing the current VERP address to something like:

w-wiki_id-sender_id-base_id-timestamp-hash(everything to the left)@wikimedia.org

by altering the exim regex a bit, so that on receival of a bounce for a UserMailer stuff, we can:

1. notify the sender that the email you just sent failed
2. add an entry to the bouncehandler_db for the failed recipient

in case of a usual echo notif, the sender_id would be something like wiki, and for a UserMailer mail, lets keep the sender user id there!

@01tonythomas: Could this get a priority, please? I'm afraid this triggers quite some confusion and reliability concerns... Thanks!

Alright. So @Legoktm was asking me how useful it would be to spend programming effort on this one.

I will try pinging @Legoktm to comment his views, which is the truth, but might not be best expressed in my words (it's something with why people suddenly started complaining about mails not reaching)

Yeah, Tony and I briefly talked about this at Wikimania. It's unclear to me whether this is a new issue, or we've only recently realized how bad the email delivery system is (my hunch)...

@01tonythomas: Could this get a priority judgement please, by setting the priority field?