What if a user on your network has recently downloaded a virus onto their computer and they are now sending out emails that contain harmful malware to other people in the office? Until you solve the infection, you need a way to temporarily prevent the infected computer from sending out emails within the network.
Thankfully, FortiMail supports customizable access controls that can automatically reject emails from sources that you know to be infected.
Access control rules, or the access control list (ACL), controls how the FortiMail unit processes email messages. When an SMTP client attempts to deliver email through the FortiMail unit, the FortiMail unit compares each access control rule to the commands used by the SMTP client during the SMTP session. So, if you wanted to prevent a known infected source from sending you email, you would set your FortiMail unit to reject emails from that source.
This recipe assumes you have already created an inbound recipient policy.