This article was previously published under Q264035
Important This article contains information about how to modify the registry. Make sure that you back up the registry before you modify it. Make sure that you know how to restore the registry if a problem occurs. For more information about how to back up, restore, and modify the registry, click the following article number to view the article in the Microsoft Knowledge Base:
256986 Description of the Microsoft Windows registry
You can configure an Exchange Server computer to use specific Transmission Control Protocol (TCP) ports for the information store, directory, and System Attendant to enable access to it through a firewall, router, or other device that blocks certain TCP or User Datagram Protocol (UDP) ports. You cannot configure the ports that will be used when the server sends a client a new mail notification packet. In a situation where UDP traffic from the server to the client is blocked, clients may not receive new mail notification. For more information about how to configure TCP/IP access to an Exchange Server computer through a firewall for Exchange 2000 Server, click the following article number to view the article in the Microsoft Knowledge Base:
New mail notification messages are sent by means of UDP packets from the server to the client. The ports used for this notification are set by the client when the client logs on to the information store.
As part of the log on process to the information store, the client tells the server the IP address and port where it expects to receive new mail notification messages. This will be a UDP port in the 1024-65535 range.
When the server receives a mail message for a mailbox that a client is logged on to, it opens a UDP port dynamically, and sends a packet to the IP address and port registered by the client logged on to that mailbox.
Because the client picks a port at startup and the server does not always use the same port when sending the notification, there is no way to predict either the source or destination ports that this traffic will use.
For clients to reliably receive new mail notification packets, you must enable traffic as follows:
Setting Value ------------------------------------------ Protocol ID UDP Direction Exchange Server --> Client Local Port >1024 Remote Port >1024
The "Client" in this table can be specifying either specific client IP addresses or the networks where the clients reside. Your filtering device documentation will have information on how to actually implement the filter.
Note Microsoft Outlook 2003 includes a registry key that allows the setting of a static UDP port for new mail notification packets. This registry key is available only in Outlook 2003 or later. You can modify the following registry key to specify a UDP port number.
Warning Serious problems might occur if you modify the registry incorrectly by using Registry Editor or by using another method. These problems might require that you reinstall the operating system. Microsoft cannot guarantee that these problems can be solved. Modify the registry at your own risk.