I still think the only way to read the documentation for parseaddr('a@b@c') is to return ('', '') - a tuple of empty strings.

The documentations says:

"Returns a tuple of that information, unless the parse fails, in which case a 2-tuple of ('', '') is returned."

Of course, it doesn't define exactly what a "failing parse" is, but I would claim that a non-RFC compliant address should fail to parse, at least for the parseaddr() interface.

I'm not concerned about inconsistencies between message_from_string() and parseaddr().  They are difference APIs.

I'll follow up on the PR, but does anybody disagree with that reasoning?