This thread has been really interesting to follow, I'm glad to have opened it :)

I would agree with Barry here, it should follow the documentation.

BUT, I would suggest to add a "strict" parameter that would throw exceptions depending on the parsing issue (missing a @, having multiple @, etc).

That way, a basic usage would return the empty strings, letting the developer know the email is invalid, and advanced case would still be possible.

By default, I think having strict set to False would be logical, since it would follow the documentation.