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What is an Exchange server? The obvious answer is that it is a server running the Exchange Server software. However, there are many Exchange Server components, and it is rare to find them all installed and operational on a single hardware platform. It is much more common to deploy specialized servers, each using one or more of the Exchange Server components. This allows you to tailor each dedicated server to meet specific requirements. For example, you can configure one dedicated server to handle user mailboxes and a separate server to handle only connectivity to other messaging environments.
There are several reasons for using dedicated servers, including:
To isolate services that use excessive hardware resources so that these services will not negatively impact other messaging services
To support a number of users or services, or both, that exceeds the capacity of a single server
To separate services with conflicting hardware configuration or tuning requirements
To limit the number of servers and services exposed to the Internet or other external networks
To provide redundancy for various messaging services
To isolate certain groups of users, such as accounting or human resources, from other users for legal reasons
The number of dedicated servers you elect to deploy will depend primarily on the set of services you choose to offer, the number of users you have, and your network topology. Some of the more common types of dedicated Exchange servers are:
Mailbox servers. A dedicated mailbox server is one that supports only user mailboxes. It supports no connectors, public folders, or other Exchange services. Deploying dedicated mailbox servers prevents users' access of their mailboxes from being impacted by other services that may demand significant server resources. Dedicated mailbox servers are recommended for all but the smallest of organizations. A dedicated mailbox server can provide reliable and predictable service to a larger number of users. Implementing dedicated mailbox servers also will facilitate the ability to designate storage groups to isolate user mailboxes.
Public folder servers. If you plan to make heavy use of public folders, you should consider a dedicated public folder server. Exchange supports features, such as anonymous public folder access, that can be designed to allow access to public folders through the Internet. If you plan to allow Internet access to your public folders, you should definitely implement a dedicated public folder server to help protect your network by restricting Internet access to the public folder server.
Outlook Web Access (OWA) servers. If you need to offer OWA to a large number of users, you can use a dedicated OWA server to isolate the OWA network traffic. If you plan to support OWA access through the Internet, you can increase network security by making only the dedicated OWA server visible to the Internet. Microsoft Internet Security and Acceleration Server publishes OWA to the Internet, which helps isolate the Exchange servers from the Internet.
Connector servers. Microsoft offers connectors to other messaging environments, including Simple Mail Transfer Protocol (SMTP), X.400, Active Directory, Lotus Notes, and Novell GroupWise. Other manufacturers provide additional connectors such as fax connectors, SAP connectors, Blackberry connectors, and others. If you expect to send and/or receive a large quantity of mail from other environments, you should implement a dedicated connector server to isolate the processor demand required to handle the large amount of traffic. You can install each of these connectors independently of each other or in combination on one or more dedicated servers.
Internet mail servers. For security reasons, your SMTP connection to the Internet should always be through a dedicated server. Your dedicated Internet servers can be configured to offer SMTP, Internet Mail Access Protocol 4 (IMAP4), Post Office Protocol 3 (POP3), and Network News Transport Protocol (NNTP) services using the protocol virtual servers.
Exchange 2000 included Instant Messaging and Conferencing. However, Exchange 2003 does not include these capabilities. Instead, Microsoft will provide Instant Messaging and Conferencing as separate products.
Of course, you can install all of the Exchange components on a single hardware platform. This is easy to do, and it may be appropriate for organizations with a small number of users and minimal messaging needs.
However, the server performance will decrease as user demand increases.
This chapter provides an overview of the more common Exchange server configurations and guidelines for managing the server components that are deployed on these servers.
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