Ah Conan, you were going to be my answer..!
Fancy popping round to have a nose at my machine....
Have gone back into Norton and tried again to set "permit". This time the pc froze.. High hopes I thought - obviously too high - Nortons Firewall still doesn't like allowing me to send / receive email.
But, Windoze is happily looking after the firewall, so I'll live with it until next update.