The final step in creating your messaging topology is to plan your topology elements in your actual deployment, as described in Understanding Messaging Topology Elements. The following figure illustrates the topology elements in the Chicago and Minneapolis offices.
Because 30 percent of the workforce is made up of third-party vendors and contractors, internal firewalls are used in addition to the external firewalls in the topology to restrict access to locations within the company. Internet MTAs are placed in the topology to route messages from the Internet and relay them across the firewall. MTAs are added to route incoming and outgoing messages. Separating incoming and outgoing messages helps to manage the high volume of message traffic. The MMP connects employees’ POP and IMAP mail clients to their mailboxes in the Messaging Servers. By using an MMP, employees don’t have to know their specific mail host when they log in, and administrators can seamlessly move employees’ mailboxes to different mail server locations.
Creating a messaging topology enables you to account for the physical and logical placement of all the elements in your deployment. Doing so ensures minimal rework of your installation.