Why does Thunderbird not immediately send incoming mail prefixed with [Norton AntiSpam] to the spam file when I have specifically set this up in the Tools?

Did you include the square brackets in your filter string? Try without them.

Had no effect, except now some come in prefaced by "alandick".

Could you forward me a message (as an attachment) that has been tagged thus?

xenos at gmx dot co dot uk

I wanted you to forward a message to me, via email, to the address I gave above. Forward it as an attachment, not inline, so I get a full copy complete with headers. I can then use it to check how it might be avoiding being filtered.

I may be able to use what you have sent, but I will need to retype everything to construct a similar message.