Summary:
See PHI785. Ref T13164. In this case, an install wants to receive mail via Mailgun, but not configure it (DKIM + SPF) for outbound mail.
Allow individual mailers to be marked as not supporting inbound or outbound mail.
Test Plan:
- Added and ran unit tests.
- Went through some mail pathways locally, but I don't have every inbound/outbound configured so this isn't totally conclusive.
- Hit `bin/mail send-test` with a no-outbound mailer.
- I'll hold this until after the release cut so it can soak on `secure` for a bit.
Reviewers: amckinley
Reviewed By: amckinley
Maniphest Tasks: T13164
Differential Revision: https://secure.phabricator.com/D19546
690a460c8e