Reckon you'll need to turn off SPA in the outgoing mail server (SMTP) settings....
Click the file menu, then Info on the left hand side, click on the account settings button, you should see a list off all the mail accounts you have(probably just the one), if you double click on the tiscali account it will open the properties for that account....
Now click on the more settings button in the bottom right, and on the page that opens click the outgoing server tab.
Now on that page take a tick out of "require secure password authentication (SPA), cick ok a few times to close everything and then try again