I don't care for overaggressive email validators myself, but if you are registering with my service using an email of ""()<>[]:,;@\\\"!#$%&'*+-/=?^_`{}| ~ ? ^_`{}|~.a"@example.org" I'll probably want you to enter something more reasonable.
Anyway just because it is valid according to the RFC, doesn't mean that it's actually a valid user's email address.
Anyway just because it is valid according to the RFC, doesn't mean that it's actually a valid user's email address.