OKk. thanks, u've been very exhaustive! Now I've scanned pop.xxxxxxxx.com with nmap and the program gives me this result:
PORT STATE SERVICE
25/tcp open smtp
80/tcp open http
110/tcp open pop3
143/tcp open imap
443/tcp open https
993/tcp open imaps
995/tcp open pop3s
Which of these is the pop port? 110 or 995? And do you know what's the difference between pop3 and pop3s in the result? thanks