The PHP

//FILE: /ajax/ajax-contact-us.phh
wp_enqueue_script('ajax-contact-us', get_stylesheet_directory_uri().'/ajax/ajax-contact-us.js', array('jquery'), 1.1, true);
wp_localize_script('ajax-contact-us', 'ajax_object', array('ajaxurl' => admin_url('admin-ajax.php')));

add_action('wp_ajax_action_send_contact_us', 'send_contact_us');
add_action('wp_ajax_nopriv_send_contact_us', 'send_contact_us');
function send_contact_us() {


	$sender_name		=	sanitize_text_field($_POST['sender_name']);
	$sender_email		=	sanitize_email($_POST['sender_email']);
	$sender_subject		=	sanitize_text_field($_POST['sender_subject']);
	$sender_site		=	sanitize_text_field($_POST['sender_site']);
	$sender_message		=	sanitize_text_field($_POST['sender_message']);


	// CHECK NECCESERY FIELDS
	if(!$sender_name) {echo '<div id="error">'.__('Please fill out your name.').'</div>';}
	elseif(!$sender_email) {echo '<div id="error">'.__('Please enter a valid email address.').'</div>';}
	elseif(!$sender_subject) {echo '<div id="error">'.__('Please enter a subject for this message.').'</div>';}
	elseif(!$sender_message) {echo '<div id="error">'.__('Please write a message.').'</div>';}
	else {


		// EMAIL TO ADMIN ON NEW QUESTION SUBMISSION
		$headers = "MIME-Version: 1.0" . "\r\n";
		$headers .= 'Content-type: text/html; charset=UTF-8' . "\r\n";
		$headers .= 'From: no-repaly@YOUR-DOMAIN.COM' . "\r\n" .
			'Reply-To: '.$sender_email . "\r\n" .
			'X-Mailer: PHP/' . phpversion();


		$to      =	'YOUR-EMAIL@YOUR-DOMAIN.COM';
		$subject =	__('A new email from site', THEME_NAME);
		$message =	__('Sent By').': '.$sender_name. "\r\n" .
					__('Sender Email').': '.$sender_email. "\r\n" .
					__('Sender Phone').': '.$sender_phone. "\r\n" .
					__('Message').': '.$sender_message;


		mail($to, $subject, $message, $headers);


		echo '<div id="success">'.__('Message Sent, thanks you').'</div>';

	}

	die(); // stop executing script
}