SMTP Routes and DNS

Use the special keyword USEDNS to tell the appliance to do MX lookups to determine next hops for specific domains. This is useful when you need to route mail for subdomains to a specific host. For example, if mail to example.com is to be sent to the company’s Exchange server, you might have something similar to the following SMTP route:

example.com exchange.example.com

However, for mail to various subdomains (foo.example.com), add an SMTP route that looks like this:

.example.com USEDNS