Sending Mail: Internal User to Another Internal User

Synopsis: Internal User > Load Balancer > MTA Outbound Relay 1 or 2 > MTA Inbound Relay 1 or 2 > Message Store 1 or 2

An increasingly more common scenario is to use LMTP to deliver mail directly from the outbound relay to the store. In a two-tiered deployment, you can make this choice.

Messages addressed from one internal user to another internal user (that is, users on the same email system) first go to a load balancer. The load balancer shields the email user from the underlying site architecture and helps provide a highly available email service. The load balancer sends the connection to either MTA Outbound Relay 1 or 2. The outbound relay reads the address and determines that the message is addressed to an internal user. The outbound relay sends the message to MTA Inbound Relay 1 or 2 (or directly to the appropriate message store if so configured). The MTA Inbound Relay delivers the message to the appropriate Message Store. The Message Store receives the message and delivers it to the mailbox.