Chapter 15 Unified Threat Management for FortiOS 5.0 : Security Profiles overview : Security Profiles components : Email filtering
  
Email filtering
FortiGuard AntiSpam is a subscription service that includes an IP address black list, a URL black list, and an email checksum database. These resources are updated whenever new spam messages are received, so you do not need to maintain any lists or databases to ensure accurate spam detection.
You can use your own IP address lists and email address lists to allow or deny addresses, based on your own needs and circumstances.