Hi Mike - thanks for your reply. I don't know how, but I somehow managed to solve the problem and this is what (I think) I did:
I went to Network Control Rules, then Tasks, then Define a new trusted network. I followed the wizard that came up and something got added to the pane - allow IP in or out on a different/extra line, or some such? Well, it worked and I can now send email again - I just hope I haven't disabled the firewall in a different way!

Babs