The following Microsoft Exchange Server core components are installed during Setup and must be running on the server at all times:
The following illustration shows how the core components interact. The information store, directory, and MTA process requests from the client and from each other. The system attendant maintains server operation and performs key functions, such as generating e-mail addresses for new recipients; it is the background process that makes sure the system runs smoothly and the mail is routed correctly.
The information store, directory, and MTA function like elements of the postal service. When you send a message, the message is delivered to a central post office called the information store. The information store then determines where the message should be delivered by looking in the directory, which is like an address book. Then, the mail carrier (the MTA) delivers the message.