Components

The server components perform actions that the client components request, such as looking up names, sending messages, and storing information in private and public folders.

Each server has core and optional components. All server components are implemented as Windows NT Server services. The core components are installed during Setup and must be running at all times. In addition, they must all reside on the same Windows NT Server computer. The core components provide the main messaging services: message transfer, delivery, and storage, and directory services.

Following are the core server components and their functions:

Directory   maintains information about an organization's recipients, distribution lists, servers, and messaging infrastructure. Other components use the directory to map addresses and route messages. The directory is automatically replicated to all servers in the organization.

Information store   provides server-based storage, holds users' mailboxes and public folders, and enforces security. The information store also replicates public folders, enforces storage limits, and delivers messages to users on the same server. It maintains information in two databases: the public and private information stores. The public information store maintains information stored in public folders. The private information store maintains all messages in users' mailboxes.

Internet Mail Service   provides connectivity to the Internet and other systems that use Simple Mail Transfer Protocol (SMTP) The Internet Mail Service can be used to establish a dial-up connection to an Internet service provider (ISP) or a remote site at specified intervals, or to connect sites within a Microsoft Exchange Server organization.

Message transfer agent (MTA)   submits, routes, and delivers messages to other Microsoft Exchange Server MTAs, information stores, connectors, and third-party gateways.

System attendant   A maintenance service that must be running for other Microsoft Exchange Server services to run. It performs the following tasks:

• Assists in running the monitoring tools by gathering information about the services running on each server in a site.
• Checks messaging connections.
• Checks directory-replication information and corrects inconsistencies.
• Logs information about messages for message tracking.
• Builds routing tables in a site.
• Generates e-mail addresses for new recipients.
• Helps enable and disable digital signatures and encryption for mailboxes.

Optional Components

The optional components provide connectivity and directory exchange with other systems, as well as advanced security. Following are the optional server components and their functions:

Advanced Security    manages security information used for digitally signing and encrypting messages sent between users.

Connectors   transfer messages between sites, organizations, and foreign systems. In addition to the Site Connector, Microsoft Exchange Server includes these connectors: X.400, Internet Mail Service, Dynamic RAS, Microsoft Mail, and Connector for cc:Mail. In addition, the Microsoft Schedule+ Free/Busy Connector enables users to exchange free and busy information.

Microsoft Outlook(tm) Web Access   enables users to access their mailboxes and public folders through a Web-based e-mail client that operates in a Web browser window.