You can list all domains used for relay.
To list an authorized relay domain
Scroll to the Settings section.
Select whether to restrict relay domains:
Any source IP address is allowed to connect to this path: Allows any domain to relay messages. Go to Step 5.
Selecting this option may make a CASS open relay. Even if the mail is not destined to the recipient’s domain, the mail is relayed, which could result in spamming.