Tentatively, my plan for this is just to let you set several "bugs" addresses, and then use Herald rules to do all the routing. We already have "is newly created" and "content source", so we'd just have to add "receiving email address", and then you could write a rule like:

When all of these conditions are met:
  [ Is newly created? ] [ is true ]
  [ Receiving email address ][ contains ][ "support@" ]

Take these actions:
  [ Add Projects ][ support ]
  [ Assign task to ][ epriestley ]

So 95% of this is untangling the config mess of inbound email. I might try to move all the related email stuff here into Application settings.

You should also be able to put #project in the email body now I think, but that's not really the same use case.

It would be sort of cool if bugs+project@phabricator.com automatically worked, but I'm not sure if that is too much magic or conflicts with something else.

See T6819 for some discussion of automatic associations.

Generally:

• If you want well-known addresses (e.g., that systems or forms in your software will submit things to), the expectation is now that you'll add them all in the application config (backend-bugs@, frontend-bugs@), and then use Herald rules to route them, associate projects, assign owners, etc.
• If you want ad-hoc association, read T6819 and then file a request. We're more likely to pursue a straightforward, explicit association syntax which works everywhere (like +#project in the body) than adding magic to addresses, though. Specifically, #project did this until recently, but it didn't actually appear to be very useful and triggered when people didn't want it to.