Thread:Project:Support desk/MediaWiki not sending email/reply (11)

Hmm. Did you try special:emailuser for WikiSysop just to check for things like does wikisysop have correct email set.

My next guess is maybe the amount of email sent to that user started to trigger spam filters or something like that.

Your server may have logs about outgoing email. If so it might be worth to check them to see if the emails make it to that point or if mw is not generating them at all.