Summary: Ref T6367. Test Plan: - Added and executed unit tests. - Sent mail to A (en_US) and B (en_A*). - Got one mail in English and one mail in ENGLISH. Reviewers: btrahan Reviewed By: btrahan Subscribers: epriestley Maniphest Tasks: T6367 Differential Revision: https://secure.phabricator.com/D13142