wordpress email hook not working

I am having trouble getting the following WordPress hook working here is the following code

//if you want none logged in users to access this function use this hook
add_action('wp_ajax_nopriv_mail_before_submit', 'send_AJAX_mail_before_submit');

function send_AJAX_mail_before_submit(){
    check_ajax_referer('my_email_ajax_nonce');
    if (isset($_POST['action']) && $_POST['action'] =="mail_before_submit"){

    //send email  wp_mail( $to, $subject, $message, $headers, $attachments ); ex:
        wp_mail('email@domain.com','this is the email subject line','email message body');
        echo 'email sent';
        die();
    }
    echo 'error';
    die();
}

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The Jquery Code

jQuery(document).ready(function(){

        jQuery('#donationForm').submit(function() {

        // send email to client before moving onto worldpay payment form
        var data = {
            action: 'mail_before_submit',
            Whatever: 1234,
            _ajax_nonce: <?php echo wp_create_nonce( 'my_email_ajax_nonce' ); ?>
        };
        jQuery.post("<?php bloginfo( 'wpurl' ); ?>/wp-admin/admin-ajax.php", data, function(response) {
                alert('Got this from the server: ' + response);
        });
        //  send data to worldpay....
       // this.submit();

        });

    });

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