ALTQ - Handling Unwanted Traffic

altq on $ext_if cbq queue { q_default q_web q_mail }

   queue q_default cbq(default)
   queue q_web (...) 

    ## all mail limited to 1Mb/sec
    queue q_mail bandwidth 1Mb { q_mail_windows }
    ## windows mail limited to 56Kb/sec
    queue q_mail_windows bandwidth 56Kb

    pass in quick proto tcp from any os "Windows" to $ext_if \
    port 25 keep state queue q_mail_windows
    pass in quick proto tcp from any to $ext_if port 25 \
    label "smtp" keep state queue q_mail

" I can't believe I didn't see this earlier. Oh, how sweet. ... 
  Already a huge difference in my load. Bwa ha ha. "

Randal L. Schwartz, http://use.perl.org/~merlyn/journal/17094