Please add following code in your theme’s (child theme’s if any) functions.php

add_filter( 'fep_filter_message_before_send', 'fep_cus_send_url', 999 );

function fep_cus_send_url( $message ) {
    if( empty( $message['message_content'] ) || $message['post_parent'] )
    return $message;

    $message['message_content'] .= '<div>';
    $message['message_content'] .= esc_url( $_SERVER['HTTP_REFERER'] );
    $message['message_content'] .= '</div>';
    
    return $message;
}

Let me know.