Yahoo and their mail filters..

[johnl at iecc.com (John Levine)]

>I suggested that probably 99% of the false positives I see could be
>avoided by just waiting until there are two or more complaints from
>the same source before firing it back as spam.

Perhaps, but different people have different heuristics.  There's
nothing keeping you from writing your own de-duper that only shows you
stuff with a count of 2 or more.

R's,
John