How to check if an email address is real or valid using PHP

Question

I found some websites that claim to verify if email addresses are valid. Is it possible to check if an email address is valid using just PHP?

<?php
    if($_POST['email'] != ''){
        // The email to validate
        $email = $_POST['email'];

        // An optional sender
        function domain_exists($email, $record = 'MX'){
            list($user, $domain) = explode('@', $email);
            return checkdnsrr($domain, $record);
        }
        if(domain_exists($email)) {
            echo('This MX records exists; I will accept this email as valid.');
        }
        else {
            echo('No MX record exists;  Invalid email.');
        }
    }
?>
<form method="POST">
    <input type="text" name="email">
    <input type="submit" value="submit">
</form>

This is what I have right now. It checks if the domain exist, but it cannot check if the user's email exist on that domain. Is it possible to do that using PHP?

Answer 1

You should check with SMTP.

That means you have to connect to that email's SMTP server.

After connecting to the SMTP server you should send these commands:

HELO somehostname.com
MAIL FROM: <[email protected]>
RCPT TO: <[email protected]>

If you get "<[email protected]> Relay access denied" that means this email is Invalid.

There is a simple PHP class. You can use it:

http://www.phpclasses.org/package/6650-PHP-Check-if-an-e-mail-is-valid-using-SMTP.html