Added support for side-by-side HTML and plaintext email building.
We can control if the HTML stuff is sent by by a new config, metamta.html-emails
Been running this in our deployment for a few months now.
Well behaved clients
- Airmail. They confuse Gmail too, though.
- Outlook (Windows + Mac)
Reviewers: chad, Blessed Reviewers, epriestley
Reviewed By: Blessed Reviewers, epriestley
Subscribers: webframp, taoqiping, chad, epriestley, Korvin
Maniphest Tasks: T992
Differential Revision: https://secure.phabricator.com/D9375