Hi Peter,
I have checked your account (ending 762) and if you go to Account Settings >> Routine Emails you will see the following warning. This indicates that we are sending mail from your address but via our own servers, this will be why they are being rejected. If you click the auto-fix link in the warning message it will set the emails to send from our own address, so they will no longer be flagged as spam.
If you still want to use your own address (not recommended with Tiscali) then you would need to either setup an SPF record or add your own SMTP details. If any of that sounds confusing, stick with the quick fix option 