How to check a valid e-mail in PHP

I’m working on  a validation e-mail address script for 3 websites i’m developing. Here is a function that can do this partially : by validating its format and then by checking if the domain it uses has any MX records registered on the DNS. function checkEmail($email){ //check format if (filter_var($email, FILTER_VALIDATE_EMAIL) == $email){ //check if [...]