FortiMail units can process email before delivering it to your company’s internal mail server. In this configuration, mail comes from an external interface into the FortiMail unit. Then the mail is processed for spam, viruses and such. The mail is then forwarded over an internal interface to a company internal mail server for internal distribution.

For redundancy, companies can configure a secondary FortiMail unit that is connected to a secondary internal mail server. In this configuration the secondary FortiMail unit is normally not active with all mail going through the primary FortiMail unit. The secondary system is activated when the external interface on the primary FortiMail unit is unreachable. Mail is routed to the secondary system until the primary unit is can be reached and then the mail is delivered to the primary FortiMail unit once again. In this configuration the mail only goes to one FortiMail unit or the other - it is never divided between the two.

If the internal mail server becomes unreachable from the primary FortiMail unit's internal interface, the primary FortiMail unit needs to stop the incoming email or the email will continue to accumulate and not be delivered.

The FortiMail unit can track the status of the internal interface. When interface tracking sees the internal interface go down, it brings down the FortiMail external interface. This stops email from accumulating on the primary FortiMail unit. If your company has the redundant secondary FortiMail unit configured, email can be routed to it until the primary FortiMail unit can be reached again. Interface tracking also brings the external interface up when the internal interface comes back up.

With interface tracking, you can set which interfaces are associated. You can also set how often interface tracking checks the status of the interfaces. This is the maximum delay before the interfaces associated with the downed interface are brought down as well.