Due to numerous mail servers out there producing bounce emails in various formats, there is always a chance of unrecognized bounce emails coming in, and the filters getting confused. We kept a variable

$wgUnrecognizedBounceNotify = null;

which can be used to notify admins on the incorrect bounce email including full-bounce-email as body[2]. To whom should we have these addressed to ?

[2] https://github.com/wikimedia/mediawiki-extensions-BounceHandler/blob/63bb101c1e279619c127e83b8922ed835b476d90/includes/ProcessUnRecognizedBounces.php#L37