Mário Andrade

So let’s create a function to allow you to check the dns record of a full email address:

function VerifyEmailAddress($email) {
    list($user, $domain) = explode("@", $email);
    $result = checkdnsrr($domain, 'MX');
    return($result);
}

This function breaks the email string example@domain.tld giving the username the the content before @ and the domain the content after the @.
If you insert an email like example@domain.tld the user would be example and the domain would be domain.tld.

After breaking the email into user and domain the function calls checkdnsrr to check is the MX records on the $domain variable returning 1 is the domain exists or 0 if the domain does not exist.

Now you need to call it when checking an email:

if(VerifyEmailAddress($email) != 1) {
    echo "The e-mail you inserted is not valid.";
}

And here you have it. You can now check if the domain of an email exists.
For complete email verification I advise you to implement the following functions:

• Check if email string inserted is a correct email for. Must have string@string.com
• Check if the email domain exists. You can use this tutorial for that
• Limit the amount of tries, for a determined period of time, a user can insert an email in order to stop possible spam bots