Depends on whether or not you want to use DCC and/or Razor. They are network checks, so they can be comparatively slow, but they're both very effective tests. (At least, if you are talking about Razor 2.6 or higher)
I would like to use them with SA. They won't affect Bayes scores?
Should I feed SPAM/HAM to postmaster?
Erm. I'm not quite sure what you mean by this... Is your postmaster hungry? :)
Maybe my concept is not clear. I don't have local mailbox except root/postmaster. SA needs to forward SPAM/HAM to some folder from Bayes training?
Seriously though, if you've got a global bayes_path and bayes_file_mode 777 you can do your training when logged in as any user.
Thank you for your recommendation.
Regards, Norman Zhang