From: Kyle Schmitt <kyleaschmitt@...>
Date: 2008-07-29T02:12:29+09:00
Subject: Re: regarding validation of email address.

On Mon, Jul 28, 2008 at 9:19 AM, Phlip <phlip2005@gmail.com> wrote:
> E-mail address validation is a FAQ in the Regular Expression discipline.
>
> You can't do it. No Regexp can successfully distinguish valid from invalid
> e-mail addresses, in all their permutations.
>
> If you want to provide a simple defense against typographical errors, such
> as omitting the @, you must write a Regexp that is too wide, and will permit
> some ill-formed addresses to slip past.
>
> --
>  Phlip
Actually I believe it _can_ be done, but it's next to useless to do so.
There's a nasty regex that claims to validate all RFC 2822 compliant
email addresses over at regular-expressions.info, and it was done so
just to show that it really is a bad idea.  The regex Is really really
hideous, but the article on why not to do it is well done.
http://www.regular-expressions.info/email.html

For those who don't want to read the article, the last paragraph is
one that should be remembered when using regexes..

"Don't blindly copy regular expressions from online libraries or
discussion forums. Always test them on your own data and with your own
applications."




--Kyle