darkeghost

Okay after doing a bunch of research I have managed to find a way to do this.

function listing_published_send_email($post_id) {

        if( 'job_listing' != get_post_type( $post_id ) ) {
            return;
        }
        $post = get_post($post_id);
        $author = get_userdata($post->post_author);
        $job = get_the_job_application_method($post);

        // Message to be sent to users.
        $message = "Put the message you want to send here";

        // Checks to see if the person who submitted the job listing is a user or a guest.
        if ($author == 0 OR $author == NULL){

            // Checks to see if the email is valid.
            if ($job->type == 'email') {
                $email = $job->email;
                wp_mail($email, "Your job listing is online", $message);
            }
            else { // The email is not valid so return.
                return;
            }
        }
        else {
            wp_mail($author->user_email, "Your job listing is online", $message);
        }
    }
    add_action('pending_to_publish', 'listing_published_send_email');
    add_action('pending_payment_to_publish', 'listing_published_send_email');

Should just be able to put this code in functions.php file and it will work.

I also happen to be looking for this answer.