Email address validation is a very common thing and it's pretty easy in php 5.2 or greater. You no longer need to use a regular expression. You can use this simple script below, making use of the filter_var function.
$email = 'email@example.com';
$validation = filter_var($email, FILTER_VALIDATE_EMAIL);
$output = 'proper email address';
$output = 'wrong email address';