[hso9791]

Regarding [1], in the favour of regexps: http://en.wikipedia.org/wiki/Regular_language

If you can't use a regexp to recognize the general case of email addresses, no finite automaton can..

[jdpage]

Yes, but there is a point at which it's better to just hand-write some code which is equivalent to the automaton, rather than trying to use a regexp.

This is what a proper email-validation regexp looks like: http://www.ex-parrot.com/pdw/Mail-RFC822-Address.html