I was playing around with Ruby on Rails and needed an email field for some application. I thought of validating the email address before actually saving it. Googled for same and got tons of results, but none of them was perfect. Few were somewhat exhaustive but horribly difficult to understand and those which were simple were  not exhaustive enough for practical use. I thought I’ll just write the regex myself and came up with the following. I have tested it for few weird cases like an email hosted on a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.a.exmaple.com (a subdomain deep down the hierarchy) etc.

^[A-Za-z0-9._%+-]+@([A-Za-z0-9-]+\.)+([A-Za-z0-9]{2,4}|museum)$

I hope it’ll be of help. And don’t forget to pen down your suggestions via comments.