使用ajax在Php中使用“email already exists”条件提交表单

I am working with ajax Php, I want to check email availability using ajax(on blur function) my code is working fine, showing whether email exists or not but my form submitting even " email already exists " message showing , I just want that form should not submit if I enter existing email, Here is my code, Where I am wrong?

<script type = "text/javascript" >
    $(document).ready(function() {
        /// make loader hidden in start
        $('#loading').hide();
        $('#email').blur(function() {
            var email_val = $("#email").val();

            var filter = /^[a-zA-Z0-9]+[a-zA-Z0-9_.-]+[a-zA-Z0-9_-]+@[a-zA-Z0-9]+[a-zA-Z0-9.-]+[a-zA-Z0-9]+.[a-z]{2,4}$/;
            if (filter.test(email_val)) {
                // show loader
                $('#loading').show();
                $.post("<?php echo site_url()?>/Register/email_check", {
                    email: email_val
                }, function(response) {
                    alert(response);
                    $('#loading').hide();
                    //$('#message').html('').html(response).show().delay(4000).fadeOut();
                    if (response.trim() == '1') {
                        $('#failuremsg').show().delay(4000).fadeOut();

                    } else {

                        $('#successmsg').show().delay(4000).fadeOut();
                    }
                });
                return false;
            }
        });

    }); 
</script>

replace the submit button on the form with

<button id="submit-form">Submit</button>

set a validated=true variable in your main code when all checks have passed

add some jquery

$( "#submit-form" ).click(function() {
  if(validated){
     $( "#yourForm" ).submit();
  }else{
   return false;
  }
};