smtpd()
  SMTP daemon service.
  
  This service can be used to start sagator as separate filtering SMTP
  daemon. Is is useful for postfix and any other SMTP daemon, which
  can use these filters.
  
  Usage: smtpd(scanners, host, port, prefork=2)
  
  Where: scanners is an array of scanners (see README.scanners for more info)
         host is a an ip address to bind
         port is a port to bind
         prefork is a number, which defines preforked process count.
           Set this parameter to actual processor count + 1
           or leave it's default (2). For multicore servers you can use
           core_count() function to use autodetection.
  
  Example: smtpd(SCANNERS, '127.0.0.1', 27)