smtpd_policy()
  SMTP policy service.
  
  This service can be used as smtpd policy service for postfix.
  
  Usage: smtpd_polixy(scanners, dbc, host, port, max_children=200)
  
  Where: scanners is an array of policy scanners
           (see README.scanners for more info)
         dbc is an database connection
         host is a an ip address to bind
         port is a port to bind
         max_children is a number defining maximal number of childrens
           for this service
  
  Example: smtpd_policy(SCANNERS, db.sqlite(), '127.0.0.1', 29)
  
  Postfix configuration example:
    /etc/postfix/main.cf:
      smtpd_recipient_restrictions=
              ...
              check_policy_service inet:127.0.0.1:29
              ...
  
  New in version 0.8.0.