User blog comment:Kirkburn/Technical Update: April 13, 2015/@comment-452-20150418194704/@comment-5275700-20150423190920

Plain text versions of the watchlist emails will be returning next week (in the Tuesday release, if we continue with two releases per week). Plain text versions will be included as more emails are updated to the new design. You should be able to resume reliance on your email client's settings in that regard, without the need for extraordinary measures.

Some other bug fixes for the new design, most notably the return of the aggregate diff link for 'compare changes', will also be part of the updates next week. Thanks to everyone for your patience as we worked through some of these issues.

SendGrid is a service used by many companies to manage both transactional and marketing emails, and it's pretty standard for links in email messages to be routed through URLs like the one 452 linked. As Dinoguy observed, Wikia has been doing this for quite a while. This provides many benefits. Analytics and trends, and it also allows Community Support to easily investigate individual reports of "I'm not getting email" and resolve such issues.