User blog comment:DaNASCAT/Technical Update: March 4, 2014/@comment-14310002-20140304234702/@comment-13301-20140330172508

Just to clarify some of the information on this (I've just found that when trying to send an email to someone):
 * Special:Emailuser is not an extension. It's part of MediaWiki core and maintained by the MediaWiki developers, and It has no known bugs. Wikia doesn't have to spend any special time on this apart from the other mailing feature on wikia, like watchlist notifications, daily wiki usage, etc
 * It doesn't require any special SMTP server other than the one Wikia is currently using for sending their spammy emails about wiki activity and watchlist notifications
 * The fact that the volume of communication on that particular tool is a very poor justification for removing it given the above points.
 * Also, if it was not used it's because Wikia completely removed it from the Oasis skin.

Now there's no way for others to communicate privately with other users (specially sysops, where this tool could be used for discussing blocks, etc) without revealing the target user's real email address.

Since a few years, Wikia is losing a lot of useful features...