I dn't believe anyone has had a chance to run a mass-test on a rule for it. But this subject came up last week or so, and the consensus at the time was that the most common forms of that in spam were also completely valid in normal email.
My impression is that this isn't something that could be used alone, but
maybe some clever analysis woudl show some other characteristic it could be
combined with to form a useful rule.
Loren
