Chapter 18: Delivering E-mail

Overview

Exchange Server's primary purpose in life is to send, receive, and store messages. Sure, it stores contacts, calendar information, and tasks, but delivering e-mail messages is its life's purpose. In previous versions of Exchange, messages that were to be delivered locally (to a user whose mailbox was on your mailbox database or another database on the same server) never actually left that particular server. That all changes in Exchange Server 2007.

The new Hub Transport server role is now responsible for moving messages from one mailbox to another, and all messages must now pass through the Hub Transport server role. No matter where your messages come from, they have to travel through a Hub Transport server before delivery to your mailbox, even if the message comes from the same storage group, in the same Exchange database, or from the mailbox right next door. This lightens the load of transport from the Mailbox server and centralizes transport to a single server role. It also allows for specialized cluster servers that do not share a database, which is covered in another chapter.

The Hub Transport server role can be on a server with any other server role, except for clustered mailbox servers and Edge Transport servers. This means that if a Mailbox server does not also host the Hub Transport server, then the entire message is transferred to the Hub Transport server via Remote Procedure Calls (RPCs), then categorized, and finally routed to the appropriate location. This is true even if that location is the mailbox database on which the message originated. This is one of the reasons that it is so critical to have a Hub Transport server in each Active Directory site that contains a Mailbox server.

The Edge Transport server is separated from the rest of the Exchange server roles because it does not communicate directly with Active Directory but utilizes an ADAM directory database that is stored local to the server. The Edge Transport server role was designed to exist in a perimeter network/demilitarized zone (DMZ) segregated from the internal network. Both the Edge Transport and the Hub Transport servers facilitate transport in an Exchange organization.

Exchange 2007 lets you do a lot with a message while it is in transit. In Chapter 13, "Managing Messages in Transit," you learned about transport rules that allow you to append disclaimers to messages, process messages based on sender or recipient, or apply corporate policies to e-mail. You can offload virus detection to Hub Transport servers. And you can even keep unwanted content (viruses, spam, or messages that violate corporate policies) from ever even reaching your Exchange servers by directing inbound mail to an Edge Transport server.

In this chapter, we will discuss message transfer from both the internal message routing perspective and the perspective of messages that are sent to/received from the Internet and how to reduce the amount of spam you receive.

Topics in this chapter include the following:

• Message routing within the organization

• Deploying an Edge Transport server

• Using a Hub Transport server for Internet mail