Ah, I remember this famous question at StackOverflow on this: http://stackoverflow.com/questions/201323/using-a-regular-ex...

The gist is to avoid regular expressions in favor for some third party library like so: http://barebonescms.com/documentation/ultimate_email_toolkit...

This, of course, becomes an issue when you want to do everything in javascript and go down the rabbit hole of regular expressions. Sort of like deciding on a pattern from assumptions as one might make the mistake of doing with names: http://www.kalzumeus.com/2010/06/17/falsehoods-programmers-b...