Exchange Server and Outlook clients

By | 21 September, 2012
images Versions of Microsoft Exchange Server and Exchange clients have various port and protocol requirements. These requirements depend upon which version of Exchange Server or Exchange client is in use.
For Outlook clients to connect to versions of Exchange prior to Exchange 2003, direct RPC connectivity to the Exchange server is required. RPC connections made from Outlook to the Exchange server will first contact the RPC endpoint mapper (Port TCP 135) to request information on the port mappings of the various endpoints required. The Outlook client then tries to make connections to the Exchange server directly by using these endpoint ports.
Exchange 5.5 uses two ports for client communication. One port is for the Information Store, and one port is for the Directory. Exchange 2000 and 2003 use three ports for client communication. One port is for the Information Store, one is for Directory Referral (RFR), and one port is for DSProxy/NSPI.
In most cases, these two or three ports will be mapped randomly into the range TCP 1024-65535. If required, these ports can be configured to always bind to a static port mapping rather than to use the ephemeral ports.
For more information about how to configure static TCP/IP ports in Exchange Server, click the following article number to view the article in the Microsoft Knowledge Base:
270836  ( ) Exchange Server static port mappings
Outlook 2003 clients support direct connectivity to Exchange servers by using RPC. However, these clients can also communicate with Exchange 2003 servers that are hosted on Windows Server 2003-based computers on the Internet. The use of RPC over HTTP communication between Outlook and Exchange server eliminates the need to expose unauthenticated RPC traffic across the Internet. Instead, traffic between the Outlook 2003 client and the Exchange Server 2003 computer is tunneled within HTTPS packets over TCP port 443 (HTTPS).
RPC over HTTPS requires that port TCP 443 (HTTPS) be available between the Outlook 2003 client and the server that is functioning as the “RPCProxy” device. The HTTPS packets are terminated at the RPCProxy server and the unwrapped RPC packets are then passed to the Exchange server on three ports, in similar fashion to the direct RPC traffic described above. These RPC over HTTPS ports on the Exchange server are statically mapped to TCP 6001 (the Information Store), TCP 6002 (Directory Referral), and TCP 6004 (DSProxy/NSPI). No endpoint mapper must be exposed when using RPC over HTTPS communication between Outlook 2003 and Exchange 2003, since Outlook 2003 knows to use these statically mapped endpoint ports. In addition, no global catalog needs to be exposed to the Outlook 2003 client because the DSProxy/NSPI interface on the Exchange 2003 server will provide this functionality.
Exchange Server can also provide support for other protocols, such as SMTP, Post Office Protocol 3 (POP3), and IMAP.


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