Last modified: 2014-05-18 14:18:59 UTC
As it turned out in https://bugzilla.mozilla.org/show_bug.cgi?id=524822#c2 , the messages from a Mediawiki installation didn't pass a sender-callback-verification on the receiving side, because there was no corresponding mail account on the sending side.
Since for good functioning of a Mediawiki installation sending receivable email messages is required, I suggest that Mediawiki checks whether the given address is really present, so that filters don't block the outgoing messages.
At most, MW's installer should verify the email address is valid, but I'm not even sure of that. It would be good to add a warning about potential pitfalls if the email address isn't valid, though.
If you need to set the email sender see $wgEmergencyContact and/or $wgPasswordSender.
I'm collecting the cases of such pitfalls at http://en.altlinux.org/Non-delivery_of_email_sent_by_automated_services_to_altlinux.org . Just in case someone is interested in turning sysadmins' attention to this problem, too, and will at least make the sysadmin and all people aware of such sites publicly. It's quite annoying to come across such a site (whose emails don't get through to you).
Not only MediaWiki is one of the popular software that often has a bad sender for the outgoing emails, but Bugzilla is, too.