Technical Tip: The RBL/ORDBL SPAM feature is blocking (or allowing) all email

Description

The FortiGate is either blocking all incoming email or letting all email onto the internal network, including Spam.

Solution

This problem can occur when an SMTP server is configured as a relay.

The corporate SMTP email server receives and sends all email to the ISP’s (Internet Service Provider) SMTP server.

The Fortigate RBL/ORDBL feature uses the connecting IP address to perform the DNSBL lookup.

In this case, the IP address will always be the same (the ISP’s SMTP server).

If this ISP’s SMTP server is on a DNSBL list as a known/reported Spammer, the FortiGate unit will tag or discard all incoming email as Spam.

If the ISP email server is not flagged as a Spammer by the DNSBL service, the FortiGate unit will not tag or discard any  incoming email as Spam.