Troubleshooting Messaging Connectivity

This section discusses how to identify and isolate message flow issues.

Problems related to message flow fall into the following two general categories:

• Message routing problems   Message routing refers to the process of directing messages to their destinations from one hop to the next. The SMTP service, with its internal transport engine, is at the core of the Exchange 2003 message transport architecture. When a message is passed to the SMTP transport engine, the routing module inside the transport engine determines the correct destination and passes the message to the next messaging component. Which messaging component the message is passed to depends on where the recipients are located, as follows:

  • Local recipients   For these recipients, the next messaging component is the Exchange Information Store service, which delivers the message to the recipient's mailbox.

  • Recipients on another Exchange server within the local routing group   For these recipients, the next messaging component is the SMTP service to send the message to the destination server. The destination server might be the recipient's home server where the mailbox actually resides or a bridgehead server that connects the local routing group to other Exchange routing groups.

  • Recipients outside of the local Exchange 2003 organization   For these recipients, the next messaging component is the SMTP service if the target messaging system is connected through an SMTP virtual server or an SMTP connector. Otherwise, the message is passed to the Exchange message transfer agent (MTA) to transfer the message. The Exchange MTA might pass the message to Connector for Novell GroupWise, or an X.400 connector.

• Message transfer problems   Message transfer problems are often the result of a configuration error or a malfunctioning connector component.

  Messages accumulating in an outbound or inbound message queue or connector store indicate message transfer problems. Exchange 2003 uses outbound message queues to pass messages to connectors. The messaging connector obtains the message, converts it to the format of the destination system, if required, and transfers the message. During the conversion process, messages are often placed temporarily in a connector store. The connector store can be located within the Exchange store or on the Exchange server's file system. For inbound traffic, the connector receives the message, converts it into Exchange format, and places it into its inbound message queue.

  If messages accumulate in a message queue, Exchange 2003 generates delivery status notifications at intervals to inform the sender that the message has not reached its destination yet. If the connector problem is permanent, the problem will result in a delivery failure later on, which Exchange 2003 indicates to the sender in a non-delivery report (NDR).

  User complaints that messages do not reach their recipients in a timely manner also indicate transfer problems. It is recommended that you monitor your bridgehead servers and messaging connectors continuously using the tools mentioned earlier in this topic, so that you can react to message transfer problems before users start noticing that their messages are delayed.

Troubleshooting Message Routing Problems

Exchange 2003 maintains routing information in the Active Directory configuration naming context. You configure the routing information by means of the address spaces and cost factors that you assign to the individual connector instances in Exchange System Manager. Address spaces are subsets of e-mail address information that are used to categorize recipients.

Table 1 lists the various types of address spaces in Exchange 2003.

Table 1   Standard address spaces in Exchange 2003

Table 1 lists examples of most general address spaces. You can also assign more detailed address spaces if you want to distribute the message traffic over multiple connector instances. In general, the Exchange transport engine chooses more detailed address spaces over general address spaces. However, it is recommended that you assign the most general address space possible to include all possible recipients in the same address space.

You can use the WinRoute tool to view message routes and connector states when you are troubleshooting problems related to message routing in an Exchange 2003 organization. The WinRoute tool extracts link state information from Exchange 2003 and presents the information in a readable format. You can download this tool from https://go.microsoft.com/fwlink/?LinkId=25049.