Troubleshooting email transmission problems is as much about knowing where to look, as it is about knowing where not to look for problems. Everyone knows to check the logs and look for event ID and event messages, but sometimes it is the overlooked or forgotten places that can yield the answers to our problems.  If you’ve been administering systems and servers for a long time then you’ve probably already had a situation like that.

Sometimes an administrator will spend countless hours of troubleshooting only to find that the answer was quite simple. It seems that one of the usually overlooked places on a server is the firewall and the port settings that it guards. Administrators should know of all the ports associated with an Exchange server to help them with their troubleshooting efforts.

Here is part two of a two part list of ports associated with Exchange Server.

Protocol: SMTP/LSA

• Port (TCP/UDP): 691 (TCP)
• Description: The Microsoft Exchange Routing Engine (also known as RESvc) listens for routing link state information on TCP port 691. Exchange server uses routing link state information to route messages and the routing table is constantly updated. The Link State Algorithm (LSA) propagates outing status information between Exchange servers. This algorithm is based on the Open Shortest Path First (OSPF) protocol from networking technology, and transfers link state information between routing groups by using the X-LSA-2 command verb over SMTP and by using a Transmission Control Protocol (TCP) connection to port 691 in a routing group.

Protocol: RVP

• Port (TCP/UDP): 80 (TCP)
• Description: RVP is the foundation for Instant Messaging in Exchange Server. While RVP communication begins with TCP port 80, the server quickly sets up a new connection to the client on an ephemeral TCP port above 1024. Because this port is not known in advance, issues exist when you enable Instant Messaging through a firewall.

Protocol: IRC/IRCX

• Port (TCP/UDP): 6667 (TCP)
• Description: Internet Relay Chat (IRC) is the chat protocol. IRCX is the extended version offered by Microsoft. While TCP port 6667 is the most common port for IRC, TCP port 7000 is also very frequently used.

Protocol: IRC/SSL

• Port (TCP/UDP): 994 (TCP)
• Description: IRC (or Chat) over SSL. IRC or IRCX over SSL is not supported in Exchange.

Protocol: X.400

• Port (TCP/UDP): 102 (TCP)
• Description: ITU-T Recommendation X.400 is really a series of recommendations for what an electronic message handling system (MHS) should look like. TCP port 102 is defined in IETF RFC-1006, which describes OSI communications over a TCP/IP network. In brief, TCP port 102 is the port that the Exchange message transfer agent (MTA) uses to communicate with other X.400-capable MTAs.

Protocol: MS-RPC

• Port (TCP/UDP): 135 (TCP)
• Description: Microsoft Remote Procedure Call is a Microsoft implementation of remote procedure calls (RPCs). TCP port 135 is actually only the RPC Locator Service, which is like the registrar for all RPC-enabled services that run on a particular server. In Exchange, the Routing Group Connector uses RPC instead of SMTP when the target bridgehead server is running Exchange server. Also, some administrative operations require RPC. To configure a firewall to enable RPC traffic, many more ports than just 135 must be enabled.

Protocol: T.120

• Port (TCP/UDP): 1503 (TCP)
• Description: ITU-T Recommendation T.120 is a series of recommendations that define data conferencing. Data conferencing is implemented on the server side as a Conferencing Technology Provider (CTP) in the Multipoint Control Unit (MCU), which is one component of the Exchange Conferencing Services (ECS). Data conferencing is implemented on the client side as Chat, Application Sharing, Whiteboard, and File Transferring in Microsoft NetMeeting.

Protocol: ULS

• Port (TCP/UDP): 522 (TCP)
• Description: User Locator Service is a type of Internet directory service for conferencing clients, such as NetMeeting. Exchange Server and Exchange  Conferencing Server do not implement a ULS, but rather take advantage of Active Directory for directory services (by TCP port 389).

Protocol: H.323 (Video)

• Port (TCP/UDP): 1720 (TCP)
• Description: ITU-T Recommendation H.323 defines multimedia conferencing. TCP port 1720 is the H.323 (video) call setup port. After a client connects, the H.323 server negotiates a new, dynamic UDP port to be used for streaming data.

Protocol: Audio

• Port (TCP/UDP): 1731 (TCP)
• Description: Audio conferencing is enabled in much the same way as H.323 video conferencing is enabled in Exchange Server. After clients connect to TCP port 1731, a new dynamic port is negotiated for further streaming data.

Protocol: DNS

• Port (TCP/UDP): 53 (TCP)
• Description: Domain Name System (DNS) is at the center of all the services and functions of your Windows Active Directory and Exchange Server. You cannot underestimate the impact that a DNS issue can have on the system. Therefore, when service issues arise, it is always good to verify proper name resolution.

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