If you were filtering based off of the subject you should switch to the List-Id header:
List-Id: RubyGems developers mailing list <rubygems-developers.rubyforge.org> _______________________________________________ RubyGems-Developers mailing list http://rubyforge.org/projects/rubygems RubyGems-Developers@rubyforge.org http://rubyforge.org/mailman/listinfo/rubygems-developers
