recipient_policy()
  Virtual recipient policy.
  
  This policy check is invoked after an "RCPT TO:" smtp command is received.
  You can use an policy scanner combination as scanner. It is useable for
  postfix's before-queue policy filter or an policy filter for milter.
  This service must be defined before service, which want to use it.
  
  Usage: recipient_policy(scanners, dbc)
  
  Where: scanners is an array of policy scanners
           (see README.scanners for more info)
         dbc is an database connection
  
  Example: recipient_policy(POLICY_SCANNERS, db.sqlite())
  
  New in version 0.8.0.