12. The method of claim 11 , further comprising using the metadata to rank the candidate signature relative to at least one additional candidate signature associated with the spam message.
13. The method of claim 12 , wherein using the metadata to rank the candidate signature relative to at least one additional candidate signature associated with the spam message comprises ranking the candidate signature based on at least one of: the ratio of misspelled words to correctly spelled words within the candidate signature; whether all text within the candidate signature is capitalized; whether the ratio of whitespace to non-whitespace characters within the candidate signature exceeds a predetermined threshold; whether the ratio of misspelled words to correctly spelled words within the candidate signature exceeds a predetermined threshold.