Viewing the greylist statuses

Greylisting exploits the tendency of legitimate email servers to retry email delivery after an initial temporary failure, while spammers will typically abandon further delivery attempts to maximize spam throughput. The greylist scanner replies with a temporary failure for all email messages whose combination of sender email address, recipient email address, and SMTP client IP address is unknown. If an SMTP server retries to send the email message after the required greylist delay but before expiry, the FortiMail unit accepts the email and adds the combination of sender email address, recipient email address, and SMTP client IP address to the list of those known by the greylist scanner. Subsequent known email messages are accepted. For details on the greylisting mechanism, see “About greylisting”.

To use greylisting, you must enable the greylist scan in the antispam profile. For more information, see “Managing antispam profiles”.

	Enabling greylisting can improve performance by blocking most spam before it undergoes other, more resource-intensive antispam scans.


	Greylisting is bypassed if the SMTP client establishes an authenticated session (see “Controlling email based on recipient addresses”, and “Controlling email based on IP addresses”), or if the matching access control rule’s Action is RELAY (see “Order of execution”).

You can configure the initial delay associated with greylisting, and manually exempt senders. For details, see “Configuring the grey list TTL and initial delay” and “Manually exempting senders from greylisting”.