spf_check()
  SPF (Sender Permitted From) checker.
  
  This scanner can be used to scan for sender's SPF records in content
  scanner or policy scanner.
  
  Usage: spf_check(hard_error=False)
  
  Where: hard_error can be set to True, if you want errors raise as exceptions,
           by default it is turned off.
  
  Example: spf_check()
  
  New in version 0.8.0.