smtp_comm()
  Primitive regexp pattern scanner for SMTP communication.
  
  For more information about this scanner see documentation for
  regexp_scan realscanner.
  
  This scanner also can be used to apply some scnanner to defined
  email adresses. For example:
      smtp_comm([['D', '^RCPT TO:.*anydomain.dom']]])
        & buffer2mbox(libclam())
  In this example, libclam() scanner is used only if mail is
  adressed to an user on anydomain.dom.
  
  Usage: smtp_comm([['VirName', 'RegExp_Pattern...', ...], ...], flags=0)
  
  Where: 'VirName' is a string, which identifies defined virus
         'RegExp_Pattern...' is a regexp pattern
         flags is an integer, which defines regular expression flags.
           By default re.IGNORECASE|re.MULTILINE is used.