system
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As I mentioned in the original post I use Outlook Express for the following email accounts:
1x MSN
1x Hotmail
2x Yahoo
1x Lineone.net (Tiscali)
The Lineone account is a leftover from the days when I had several ISPs and paid for internet access by the minute. I just use it to download stuff because I could never get ‘send’ to work owing to my using an AOL ISP rather than a Tiscali/Lineone one.
Anyway, I noticed in the Avast! help files (Setting up the Mail Protection: Manual Setting of Mail Protection) that it says:
additionally, it is possible to set the login name in the form #smtp.tiscali.com, which means that the mail will be sent using the server smtp.tiscali.com without any authentication.
I tried it and now I can send on smtp.lineone.net!
I’m not at all sure why it should start working now but I’m pretty pleased about it - even if I never use it anyway 
John