Just a quick note to the world - Gmail (googlemail in the UK) works admirably as a spam filter.
I have a couple of my own domains and was drowning in spam (junk) email. So far I have been forwarding all of my email through gmail and then back to myself for a fortnight. Statistics so far are approximately (it's the false negatives that are approximate as I have not been labelling them as such to keep count of them):
1,248 Total emails received
210 Good emails received
1,038 Spam emails received (vast majority being identified by Gmail as spam - see below)
2 False positives (i.e. good emails inappropriately marked by Gmail as spam - both were circulars (one Japanese, one English), but ones I wanted)
~25 False negatives (i.e. spam emails not appropriately identified - mainly delivery failure messages where the spoofed from address was at my domain)
This includes email (spam and valid) in both Japanese and English, so I do not think these results are too bad.
Thanks to
cairmen for initially making the post that put me on to this. I've not seen him post his promised results, but hope others find the above useful.