Did you mean "exactly one of which is @"?

That's not the rule that 'Freak_NL posted, which is why I read your rule as "at least one of which is @".

And, besides, as others have pointed out, "exactly one of which is @" is incorrect. Valid email addresses can have multiple @ characters.

I am not Freak_NL. I am also not interested in participating in the deviancy of people who choose to use email addresses containing quoted strings which themselves contain @s. Anyone who wishes to engage in such self-abuse is entirely free to do so. I don't feel myself constrained to play along.

Well, okay, but you've now stepped away from the goal of allowing all valid email addresses, and are now restricting email addresses that don't fit your personal opinion of what a good email address is, which is at odds with what the actual rules for valid email addresses are.

Your opinion might have a lot of reasons to support it, but it does not seem to be consistent with the position you were advocating. I am interested in not validating email addresses, because of your convincing argument that I should not. And now you want me to validate them.

Where did I claim that as my goal? If somebody just has to be a wiseass, that's fine, but I don't mind making him unhappy, because trying to make him happy along with everybody else will make me very unhappy indeed. If I can keep from making myself unhappy, and keep from making unhappy anyone who doesn't just have to be a wiseass, I'm willing to call it a day.