In general, we have an issue now where email addresses can get shadowed. For example, if you have a user named bugs and also configure a bugs@ address, both will accept mail sent to bugs@.

Currently, this will throw an exception which does not have many details about why the collision is occurring. See https://github.com/facebook/phabricator/issues/480.

I think we should probably pursue a two-part solution to this:

• Improve the error message so it shows which receivers were willing to accept the mail, and why.
• Provide a non-colliding disambiguation address for users, like user+bugs@..., and mention it in the exception.

Also, possibly, we should:

• Raise a setup error for all user-configured email addresses if more than one receiver accepts them? Specifically, when you configure a mailing address for bugs@, we can resolve a fake mail and see if it hits more than one receiver, then let you know you've shadowed something.