Email Validator Service in PHP. Can be used to validate if email exists on mail server. Just not validate only syntax but all email infrastructure.
Must be run like a service. Calling address like this http://domain.com/validate.php?q=name@domain.com next you can get result using an ajax call in jQuery:
$.ajax({
url: "http://domain.com/validate.php",
data: { q: "name@domain.com"},
dataType: "json"
}).done(function(data) {
alert(data.is_valid);
});