The ISP's Tech Dept helped me get out of the hole. Advice was "It looks
as if your mail client is set to use a username and password for
authentication for sending emails. In tools > account settings there should be an option to turn it off for outgoing server." Eventually found and unticked the box and, if this gets to the list, it's worked.
BUT; since I have never visited that page, how did my system get the setting changed, during the course of yesterday evening?
Incidentally, Avast sent me a couple of virus attack warnings, after the email problem started. I'm quite impressed by Avast.
If you don't receive this message, no doubt you'll let me know............
Gerry Winskill gwinsk@xxxxxxx