This is much more complex than it looks. I'd trust either of these before I trust those simpleton attempts, but it looks like some of them may be complete. Too hard to read the site for the longer ones though to actually find out (why is the regular expression in a little 2 line scrollable area? And why are they are not encouraging the use of extended syntax that can be commented?)

http://www.regular-expressions.info/email.html http://search.cpan.org/~rjbs/Email-Address-1.889/lib/Email/A...

As I've argued everywhere I see this sort of thing, this does not validate email addresses.

If I don't want you to have my email address, you'll get n.o.thanks@microsoft.com and that will fly through any shape validation, domain validation, character checks, any regex you can think of.

It still wont be my email address. If people aren't giving you valid email addresses, reassess your site and consider why instead of throwing technology at the alleged problem.