Concepts and workflow : How FortiMail processes email : Access control rules
 
Access control rules
The access control rules allow you to control how email messages move to, from, and through the FortiMail unit. Using access control rules the FortiMail unit can analyze email messages and take action based on the result. Messages can be examined according to the sender email address, recipient email address, and the IP address or host name of the system delivering the email message.
Each access control rule specifies an action to be taken for matching email.
For information about configuring access control rules, see “Configuring access control rules” on page 297.
See also 
Email domains
Recipient address verification
Disclaimer messages and customized appearance
Advanced delivery features
Antispam techniques
Order of execution