Incoming email messages consist of messages sent to the protected domain recipients (RCPT TO in the email envelope). For example, if the FortiMail unit is configured to protect the SMTP server whose domain name is example.com, the FortiMail unit treats all email messages sent to example.com as incoming email.

Outgoing email messages consist of messages sent to recipients (RCPT TO in the email envelope) on domains that the FortiMail unit is not configured to protect. For example, if the FortiMail unit is not configured to protect the domain example.com, all email messages sent to recipients at example.com will be treated as outgoing email, regardless of their origin.