I remember reading the opinion that one need only verify that an email address is an email address by answering, "Does it have an '@'?". Yes? Email address. No?

I remember reading the opinion that one need only verify that an email address is an email address by answering, "Does it have an '@'?". Yes? Email address. No? Try again. Perhaps it is nice to ask a question one step above the email verification: How much responsibility does//should the user have, how much responsibility does//should the designer have, in ensuring the user's email address as valid?