Nice idea. But a blind implementation of the grammar set out in the RFC is not performant. It's better to drop the obsolete syntax rules and folding white space. I have yet to see a user legitimately try to input an email with a comment mid-domain.

I implemented this in Ruby a while back, but I also went the next step and added a DNS check for a MX record. That way you can ensure there's a mail server to receive an email. Heck, I even wrote a blog post about it.

http://stevenkaras.github.io/blog/verifying-email-addresses

We've had pretty good feedback so far, but I've also spotted a few emails that people enter that are clearly fake (e.g. asdf at test.com).