Part of lp.services.mail.interfaces View In Hierarchy
For example, in email address 'firstname.lastname@example.org', 'bugs.launchpad.ubuntu.com' is the email domain.
The handler should be registered as a named utility, with the domain it handles as the name.
The 'to_address' is the address the mail was sent to. The 'filealias' is an ILibraryFileAlias. The 'log' is the logger to be used.
Return False if to_address does not exist/is bad. Return True if the mesage was processed, successfully or unsuccessfully. This includes user or input errors. Programming errors should cause exceptions to be raised.