The main one that gets passed around will match the weirdness fine. In fact, it probably matches things you don't want, anyway.

A signin/registration form really only needs to do sanity checks to get rid of obviously bad addresses. You'll have to send a round-trip email confirmation message to make sure the email is real, anyway, so why bother going into great detail? Just check that there's an '@' symbol and a dot in the domain. Most of the rest is wanking off.