Eudora Error 706 - Won't Send Mail

Hello. I seem to be having a problem sending (not receiving) mail through my Eudora. It's the free version of 6.2.3, which I upgraded to 6.2.4, but it still won't send outgoing mail. Instead, I receive an error that reads, "TCP/IP Error. 706; Lost Connection to the Server." I tried unticking the "Allow Authorization" in the Sending E-mail box in Settings, and that doesn't work either. Does anyone know what else to do? And if I have to migrate to another e-mail provider, does anyone recommend one that would take my old Eudora e-mails? Thanks so much.

PowerBook G4 12" Mac OS X (10.4.3)