Mail Server
Mail ServerWhen one first tackles the scheme of getting Internet mail delivered to their mail system, you are very speedily pointed to the need for getting an Mx narrative published within your domain's communal Dns zone. It is this narrative that tells all of the other mail servers on the planet where to route email destined for your domain.
Mail ServerWhat most do not tell you is the point of getting both the forward (A record) and reverse (Ptr record) Dns entries right for the server that is the send connector. In some cases this is the same server as the receive connector, but it does not need to be. It is very prominent that any server that is configured as an Internet Send Connector have both a forward (A record) and reverse (Ptr record) published in Dns, and that these records exactly match what you have entered in the Fqdn field on the normal tab of your Send Connector. If this one server is hosting both the send and receive connectors, the Mx narrative should also point to this same name. If your assosication accepts mail for more than one domain, simply point the Mx narrative in each domain to the same Fqdn. There is no requirement that an Mx narrative point to a server in the same Dns domain as the Mx record.