Each Exchange server has a Protocols container that contains the HTTP, Internet Message Access Protocol version 4 (IMAP4), Network News Transfer Protocol (NNTP), Post Office Protocol version 3 (POP3), Simple Message Transfer Protocol (SMTP), and X.400 protocol objects. Each object provides a virtual server to messaging clients using that protocol.
HTTP Support
HTTP is the underlying protocol used by the World Wide Web. HTTP defines how messages are formatted and transmitted, and what actions Web servers and browsers take in response to various commands. Microsoft Exchange 2000 Server supports HTTP and WebDAV to provide more functionality for general data access.
Document access - HTTP and WebDAV support a collaborative environment in which users can edit documents; protect updated data from being lost; collect resources in a common folder; move or copy files; and modify information about files, such as author, date of creation, and related file links.
E-mail access - HTTP and WebDAV can be used to access mailboxes and messages; notify users that new e-mail has arrived; and allow users to move, copy, or delete e-mail on the server.
Application access - HTTP and WebDAV are also referred to as standards-based application layers. Mailboxes and public folders are exposed through a unique URL, allowing custom applications to retrieve data directly from Information Store.
Microsoft Exchange 2000 Server provides support for WebDAV through HTTP virtual servers. The folder contents the HTTP virtual server displays are converted to Web pages and sent to a user's browser by Microsoft Internet Information Services (IIS).
IMAP4 Support
Internet Message Access Protocol version 4 (IMAP4) allows a client to access messages in private and public folders on a server. Users with an IMAP4 client can access mail in their Microsoft Exchange 2000 Server mailbox without downloading the entire mailbox to a specific computer.
A single client can access multiple mailboxes to retrieve specific messages or portions of a message, such as an attachment. IMAP4 clients can also search a mailbox and store flags to identify messages that have been read. IMAP4 does not send mail. This functionality is handled by Simple Mail Transfer Protocol (SMTP).
NNTP Support
Network News Transfer Protocol (NNTP) is an application protocol that is used over TCP/IP networks. NNTP defines a set of client and server commands used to access newsgroups.
Microsoft Exchange 2000 Server uses NNTP to enable Microsoft Outlook users to participate in online discussions over the Internet. Exchange also enables users running client applications that support NNTP to access newsgroup public folders on computers running Exchange.
Users can read and post items, such as messages and documents, to NNTP newsgroups that are represented in Exchange as public folders; for example, scientists can exchange research information by posting messages to a newsgroup public folder for their area of interest. Other scientists around the world can read and respond to items in the newsgroup. Items in newsgroups can be replicated to Usenet host computers through newsfeeds.
POP3 Support
Post Office Protocol version 3 (POP3) allows a client to retrieve a specific user's mail from the server. POP3 clients can access only their server Inboxes and cannot access other public or private folders. POP3 is not intended to provide full manipulation of mail on the server. Although messages can be left on the server, mail is usually only downloaded and then deleted. POP3 does not handle sending mail. This functionality is handled by Simple Mail Transfer Protocol (SMTP).
SMTP Support
Simple Mail Transfer Protocol (SMTP) is the Internet standard for transporting and delivering electronic messages. Based on specifications in Request for Comments (RFC) 821 and RFC 822, Microsoft SMTP Service is included in the Windows 2000 operating system.
Microsoft Exchange 2000 Server expands Microsoft SMTP Service, enhancing the basic delivery functions of the protocol without compromising its compatibility with other messaging systems. Exchange gives administrators greater control over the routing and delivery of messages, and provides secure access and channels for managing the service.
Before You Begin 
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