The Nightmare of Port 110: Your help is required.

Recently I decided to open an E-mail-account at yahoo. Apparently easy. Apparently! Because it doesn't work.
I've tried everything, but the error that always appears when I try to send E-Mails is this one: 0x800CCC0E. Meantime I've consulted friends, books and websites. No help. The only thing I found out is that this means that port 110 is already occupied. But by what?
Therefore I hope somebody on listology could help me with this.
Actually the E-Mail-account is correctly configured (smtp, pop3, etc.), the password and user name correct, the firewall desactivated (as required), etc.
Thanks in advance...
A very desperate 1922...