Unfortunately, email format validation (similar to HTML email) is somewhat of a black art:

http://haacked.com/archive/2007/08/21/i-knew-how-to-validate...

http://girders.org/blog/2013/01/31/dont-rfc-validate-email-a...

Of course one could always just go with RFC822 and this little regex:

http://www.ex-parrot.com/pdw/Mail-RFC822-Address.html