You know, I really think at this point that the random historical crap that's technically legal in an email address should be treated the same as if you walked into a restaurant and tried to order in Latin. It's time to retire a lot of it and tell people to move on.
That doesn't change the fact that a lot of validators disallow common, everyday things like + tags or even . characters. The only good way to be sure is to make sure the address contains an @ SOMEWHERE other than the last character (.+@.+, maybe), and then send a validation e-mail.
