Hi Battista,
Have used PEC once or twice, but mainly ordinary e-mail if any.  PEC is supposed to be, I  think, like sending a registered letter.  Makes little differance as I don't always get a reply anyway. As a matter of general interrest.  I do follow up e-mails if after time I don't get a reply, but sometimes they never reply and there are people on this posting who must think I am not interested in their postings because they don't get a reply.  Its quite the opposite.  Its notorious here trying to get info sometimes.
Steve