Mail Folder Analyzer Revisited

• We couldn't get any improvement from letter_histogram

     %Time ExclSec CumulS #Calls sec/call Csec/c  Name
      63.7   0.830  0.829    109   0.0076 0.0076  main::letter_histogram
      13.8   0.180  0.180      1   0.1800 0.1800  Mail::Util::read_mbox
      4.61   0.060  0.130      3   0.0200 0.0432  main::BEGIN
      4.61   0.060  0.887    109   0.0005 0.0081  main::handle_message

• Maybe look into read_mbox now?