It's true. PHP5.2 (I believe...) has a bug where [email protected], but a period cannot be the last character in the local part.

I've taken to using a multi-step method for validating an email...

$email = $_POST['email'];
if (filter_var($email, FILTER_VALIDATE_EMAIL)) {
} else if (strpos($email, '@') !== false) {
} else {

The basic premise is: the only darn thing that can really validate an email is the receiving mailserver. Offering helpful feedback saying it doesn't *look* right is as far as I go (if it has an '@' in it.) After all, before they can setup their account they do have to click the link I send to their email.