The Carrier-enabled FortiGate unit detects duplicates by keeping a record of all the messages travelling on the network and comparing new messages to those that have already been sent.

Rather than save the messages, the FortiOS carrier creates a checksum using the message body and subject. This serves as a fingerprint to identify the message. If another message with the same message body and subject appears, the fingerprint will also be the same and the Carrier-enabled FortiGate unit will recognize it as a duplicate.

By creating and saving message fingerprints instead of saving the messages, the Carrier-enabled FortiGate unit can save resources and time.