http://www.virusbtn.com/news/2012/02_15.xml
'Hotmail and Gmail have best spam filter' says Cascade spam test
Comparative test did not take false positives into account.
Researchers from Cascade Insights performed a comparative spam filtering test on the three major webmail providers and concluded that Hotmail performed best, shortly followed by Gmail, with Yahoo! a distant third.
The full report, which includes a detailed description of the methodology used, can be download as a PDF here.