You know that Exchange 2000 and Windows 2000 make heavy use of TCP/IP. But do you know exactly how Exchange 2000 uses TCP/IP or what ports and protocols it uses? Having this information can come in handy if you implement a firewall on your network or if you want to troubleshoot communication problems on your Exchange server. In this Daily Feature, we’ll take a look at the TCP/IP ports and protocols that Exchange 2000 uses.
This Daily Feature is only going to discuss what ports and protocols Exchange 2000 uses. It’s not going to go in depth about the structure of TCP/IP, what ports are, or how they work. For a discussion of TCP/IP, download TechRepublic’s TCP/IP primer.
Port of call
Applications communicate with Exchange 2000 services using specific TCP/IP ports. When Microsoft designed Exchange 2000, it used Internet standards for TCP/IP communication, so you’ll probably recognize the ports and services immediately. Table 1 shows some of the ports, protocols, and services that Exchange 2000 uses.

Table 1
Port Protocol/Service Description
25 SMTP (Simple Mail Transfer Protocol) Exchange uses SMTP for almost all of its e-mail communications. SMTP support is supplied by IIS (Internet Information Server) and not directly by Exchange 2000 itself.
53 DNS (Domain Name System) Exchange uses DNS to resolve servers that it’s going to send mail to.
80 HTTP (Hyper Text Transfer Protocol) Exchange uses HTTP in conjunction with Outlook Web Access (OWA). You also need it to make Exchange System Manager work properly. HTTP is supplied by the World Wide Web Publishing Service as part of IIS.
80 RVP (Rendezvous Protocol) Exchange 2000’s Instant Messaging uses port 80 and the RVP protocol as the basis for communication. After initiating communications on port 80 through the server, the client switches to an unused port above 1024.
102 X.400 MTA (Message Transfer Agent) Exchange uses port 102 to transfer messages to other X.400-based e-mail servers.
110 POP3 (PostOffice Protocol) This is the standard port used by e-mail programs such as Outlook Express, Eudora, pine, and PMMail to access your Exchange server.
119 NNTP (Network News Transport Protocol) Exchange uses this port to communicate with Usenet servers. It also enables Usenet clients, such as Outlook Express and Gravity, to access public news folders on your Exchange server.
135 RPC (Remote Procedure Call) Exchange uses port 135 as the RPC Locator Service. To use RPC traffic properly, Exchange requires that other ports be activated as well. Exchange 2000 uses RPC for such things as its Routing Group Connector and various administrative operations.
143 IMAP4 (Internet Message Access Protocol) Like POP3, this service runs as a part of IIS, not Exchange. However, Exchange 2000 uses it to communicate with IMAP4 e-mail clients.
379 LDAP (Lightweight Directory Access Protocol) Port 379 is one of several LDAP ports that Exchange uses. Exchange uses port 379 for its Site Replication Service.
389 LDAP Exchange uses port 389 with LDAP for access to Active Directory, Active Directory Connector, and the Microsoft Exchange Server 5.5 directory.
390 LDAP Port 390 isn’t a standard LDAP port. Exchange uses port 390 as an alternate port in an environment where you have Exchange 5.5 server running on a Microsoft Windows 2000 Active Directory domain controller. It prevents Exchange 5.5 LDAP requests from colliding with ones that would otherwise occur on port 389.
443 HTTP over SSL (Secure Sockets Layer) If you use SSL to access your Exchange server, it will use this port for HTTP access. For SSL to work, you’ll need to have an SSL certificate installed on your computer. This is true for all of the SSL protocols that follow.
522 ULS (User Locator Service) Conferencing clients, such as NetMeeting, use ULS as a directory service.
563 NNTP over SSL This port allows NNTP communication like port 119; however, this protocol ensures secure Usenet communication using SSL.
636 LDAP over SSL This port allows LDAP communication like port 389; however, this protocol ensures secure LDAP communication using SSL.
691 SMTP/LSA (Link State Algorithm) Exchange’s Routing Engine uses port 691 to transmit routing link state information. This information helps route messages and the routing tables.
993 IMAP4 over SSL This port allows IMAP4 communication like port 143; however, this protocol ensures secure IMAP4 communication using SSL.
995 POP3 over SSL This port allows POP3 communication like port 110; however, this protocol ensures secure POP3 communication using SSL.
1503 T.120 T.120 is a protocol that’s entirely concerned with data conferencing.
1720 H.323 (Video) call setup Exchange uses H.323 for multimedia conferencing. Clients initially connect to the server using H.323 at port 1720; the server then randomly creates a different port for the clients to communicate on and switches them to that port.
1731 Audio Call Control Exchange uses Audio Call Control the same way it does H.323 video.
2980 Instant Messaging Service Exchange uses port 2980 as the default port to establish communications between instant messaging clients, such as MSN Messenger.
3268 LDAP Exchange uses port 3268 as a listening port for Active Directory’s global catalog.
3269 LDAP over SSL This port enables SSL access to the Active Directory global catalog.
6667 IRC/IRCX (Internet Relay Chat) Port 6667 is one of the common ports used for IRC communication. You’ll need it if you’ve enabled chat services on your Exchange server. Other common IRC ports include 6666, 6668, 6669, and 7000. IRCX stands for IRC Extended, which is a special version of IRC supported by Microsoft.
Exchange 2000 uses these TCP/IP ports for communication.

As you know, Exchange has many new features. Through its use of standard Internet protocols, Exchange makes thorough use of TCP/IP ports. Knowing which ports do what can be useful when you try to troubleshoot communication problems with Exchange 2000.