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Connections Between Microsoft Exchange Servers

Microsoft Exchange Server computers within a site communicate with each other automatically using RPCs and named pipes. Because there are many options for connecting servers, configuration and network problems can prevent communication.

The MTA queue is growing.

Reasons Actions

There is not enough bandwidth to support the traffic. Use a network analyzer to check network usage.

The destination MTA is down. Use a server monitor and Performance Monitor to determine if the services are running and if mail is being processed.

The network is down between MTAs. Use the Ping or Net Use command from one server to the other to determine if they can communicate with each other.

Reasons	Actions
There is not enough bandwidth to support the traffic.	Use a network analyzer to check network usage.
The destination MTA is down.	Use a server monitor and Performance Monitor to determine if the services are running and if mail is being processed.
The network is down between MTAs.	Use the Ping or Net Use command from one server to the other to determine if they can communicate with each other.

There are problems with mail between sites.

Reasons Actions

The address space was defined incorrectly. Use the Administrator program to change the address space for the connection.

One of the MTAs is down. Use a server monitor or Performance Monitor to determine the status of the MTA. Message queues are helpful in determining the problem. A long queue can indicate a problem with the physical connection between servers, a server or MTA configuration error, or an incorrectly configured connector.

Mail is not scheduled to be transferred between sites at this time. Check the Schedule property page for the connector.

Site-to-site communication is configured correctly, but the transport is not routed between sites on the wide area network (WAN). Use network tools to test connectivity and the transport network protocol between bridgehead servers in the sites. Change the supported network protocol or reconfigure the network. An SMTP protocol log is available for Internet mail. For more information, see Chapter 4, "Troubleshooting Tools and Resources."

Mail is returned to sender because of size. Check the NDR for details. If the recipient is a Microsoft Exchange Server mailbox, check the recipient's Inbox Assistant for advanced rules limiting the size of mail sent.

Message transfer was working, but it stopped after a change in network configuration. Use network tools to test for network connectivity using the transport network protocol between the bridgehead servers in the sites. Change to a supported network protocol or reconfigure the network.

Reasons	Actions
The address space was defined incorrectly.	Use the Administrator program to change the address space for the connection.
One of the MTAs is down.	Use a server monitor or Performance Monitor to determine the status of the MTA. Message queues are helpful in determining the problem. A long queue can indicate a problem with the physical connection between servers, a server or MTA configuration error, or an incorrectly configured connector.
Mail is not scheduled to be transferred between sites at this time.	Check the Schedule property page for the connector.
Site-to-site communication is configured correctly, but the transport is not routed between sites on the wide area network (WAN).	Use network tools to test connectivity and the transport network protocol between bridgehead servers in the sites. Change the supported network protocol or reconfigure the network. An SMTP protocol log is available for Internet mail. For more information, see Chapter 4, "Troubleshooting Tools and Resources."
Mail is returned to sender because of size.	Check the NDR for details. If the recipient is a Microsoft Exchange Server mailbox, check the recipient's Inbox Assistant for advanced rules limiting the size of mail sent.
Message transfer was working, but it stopped after a change in network configuration.	Use network tools to test for network connectivity using the transport network protocol between the bridgehead servers in the sites. Change to a supported network protocol or reconfigure the network.

There are problems with mail delivery within a site.

Reasons Actions

The MTA or information store is down. Use a server monitor or Performance Monitor to determine if there is a problem. Check the Windows NT application event log on that server for the cause of the problem before trying to start the service.

A transport is not routed between servers on the LAN. Install a network protocol that is routed within the LAN, change the network to route the common network protocol, or move all servers to the same LAN segment. The latter can reduce performance by increasing network traffic on that LAN segment.

The network is down between MTAs. Start a link monitor to determine if the MTAs can communicate with each other on the network.

Reasons	Actions
The MTA or information store is down.	Use a server monitor or Performance Monitor to determine if there is a problem. Check the Windows NT application event log on that server for the cause of the problem before trying to start the service.
A transport is not routed between servers on the LAN.	Install a network protocol that is routed within the LAN, change the network to route the common network protocol, or move all servers to the same LAN segment. The latter can reduce performance by increasing network traffic on that LAN segment.
The network is down between MTAs.	Start a link monitor to determine if the MTAs can communicate with each other on the network.