User Agents in an Exchange Server 2003 Organization
User agents are messaging clients that the recipients use to access their mailboxes on the server running Exchange Server. Exchange Server 2003 supports several different client access protocols. The following table lists the supported messaging protocols.
Supported messaging protocols in an Exchange Server 2003 organization
| Protocol | Description |
|---|---|
MAPI |
MAPI clients provide the most functionality. With a MAPI client such as Outlook, you can access the contents of all folders in a mailbox and on the default public folder store. MAPI clients use remote procedure calls (RPC) to connect to the server running Exchange Server. Exchange Server 2003 also supports RPC over HTTP when running on Windows Server 2003. Windows Server 2003 provides the RPC over HTTP infrastructure. Client and server are not aware of the protocol encapsulation. For more information about RPC over HTTP, see the Microsoft Knowledge Base article 833401, "How to configure RPC over HTTP on a single server in Exchange Server 2003." |
HTTP |
Exchange uses HTTP to provide access to the message store through Outlook Web Access, Exchange ActiveSync, and Outlook Mobile Access. |
POP3 |
POP3 is a mail retrieval protocol that provides the most basic access to Exchange. POP3 allows a user to access messages in the inbox folder of their mailbox. |
IMAP4 |
IMAP4 is a flexible mail retrieval protocol. You can use an IMAP4 client to organize your messages on the server. You can move messages from folder to folder and preview the contents of messages before you download the entire message or a selected portion of a message, such as an attachment. |
NNTP |
NNTP is used for accessing newsgroups. You can configure Exchange to publish portions of the public folder hierarchy and make them available to NNTP clients. |