Safari 5 and Google Chrome 6-8 will not accept invalid email address input but, unlike the other browsers, will not help the user correct the error.A very quick snippet today because I've told two people to use this approach in the last few days and both of them told me they didn't know about it.Check out this list for tests (both failed and succeeded) of the regex used by PHP's is the best option.
Instead, it's better to make sure the address has all of the required parts of an email address (user, "@" symbol, and domain), then verify that the domain itself exists.
There is no way to determine (server side) if an email user exists for an external domain.
FILTER_VALIDATE_EMAIL will erroneously balk at email addresses with long domain names (64 characters or more), and at email addresses with escaped characters (such as "me\"@example.com").
Now that you have your easy answer feel free to read on about email address validation if you care to learn or otherwise just use the fast answer and move on. Trying to validate an email address using a regex is an "impossible" task.
Validating email is a very important point while validating an HTML form.