Hello Fulvio Di stefano and Riba,
Yes Riba you are right it's easy but needs some knowledge for move it. If you want you may move it yourself: ftp://plugins>>massmailer_newsletter>>block.tpl take all code from this file and insert to ftp://templates>>your_template>>tpl>>footer.tpl
But if you are in doubt create a ticket and we will move it free for you
(include ftp access details in ticket also).