DaWolf didn't indicate what purpose the email validator was going to be used for. That is why I said "context is important". I should likely have said without knowing the context, it is impossible to say how close to the RFC you need to get. I gave two examples in my reply to merlyn of where local context would be a factor, but I admit that it is just as probable that the form was to validate the "from" address of a form mailer and should be full RFC compliant.

Now that the context is known, the possibilities I presented are pointless.