Does the Mirapoint or RazorGate inbound message rounder (IMR) pay attention to MX records when looking up the Mail Access Server? In other words, when a user:mailroutingaddr query returns a hostname, does the IMR look for MX records by that name, or just an A record before making the connection? In the case of an outbound message router (OMR), is the hostname treated in the same way?
Assuming LDAP routing, there is by default no MX lookup on the IMR. This behavior may be changed with the following setting:
Smtp Set Ldapmxrouting On
If you are using Distribution List routing (not recommended), the IMR also pays attention to MX records. The OMR does not use MX records. In the case of multiple A records, round-robin DNS rotates IP addresses and the mail is delivered.