CA Gateway Security provides an email routing schema that distinguishes between incoming and outgoing email routing based on email address domains. This is comparable to nslookup MX logic.
For incoming and outgoing email, you can define domain-specific email servers or email servers for all domains or other domains not explicitly defined in the SMTP Relay Configuration dialog. You can define one or more email (relay) servers for each domain.
If you specify more than one relay server, CA Gateway Security processes the list in the specified order until relaying to a server succeeds.