In CASS 2.0, junkstore 7.3.5, there is a new feature called relay domain is introduced to relay for domains to avoid open relay issues.
A new feature called “Relay domain” (for incoming email flow) has been introduced in 7.3.5 junkstore version. Using this feature we specify the list of domains can be allowed for relay by CASS. Earlier we use to change the receive connector settings to avoid “Open relay” issues, now the configuration can be done in AntispamRelay domains.
What is an open relay?
An open relay is a SMTP server configured in such a way that is allows a third party to relay (send / receive email messages that are neither from nor for local users). Therefore, such servers are usually targets for spam senders.