    Can the user send any emails at all? Is nondelivery restricted to a subset of users?

    Does the user receive a delivery status notification? If so, what is the delivery code?

    Is the recipient in the same Exchange organization or in a different organization (presumably on the Internet)?

    How close do messages get to their destination?

    What is the messaging path between the end user and the recipient?

These questions, though relatively simple, conceal a bewildering list of possible root causes. Consider the impact on message delivery on the following:


DNS Failure

    Hub Transport servers can't locate A records and therefore can't reach next-hop servers.

Site Link Failure

    No site link exists between sender and recipient.

Transport Failure

    All of the Hub Transport servers in the user's site are inaccessible.

Transport Agent

    A transport rule prevents this email from reaching the recipient (either because of sender restrictions, content restrictions, or recipient issues).

Mailbox Limits

    The recipient's mailbox is full, but nondelivery reports do not reach the sender for whatever reason.

Messages Stuck in Queue

    A transient failure has temporarily stopped messages at a back-off location.

Back Pressure

    A Hub Transport server is temporarily throttling message delivery due to resource constraints.

This isn't even an exhaustive list, but it includes a wealth of possibilities. Now, there are few listed here that you would probably detect by performing the basic troubleshooting steps we covered earlier in this chapter (like DNS failure or transport failure). We'll begin with a simple cmdlet to check basic mail flow, which is typically the first step in locating undelivered messages, and then move on to message tracking and agent logging.

Read more at http://guides.programming4.us/technology/troubleshooting-exchange-server-2010---troubleshooting-mail-flow-(part-1)---queue-viewer-in-the-emc-.aspx#5F1ruTfRiWHca8lq.99

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To use the EMS to enable or disable message tracking and to change the path to the message tracking log, you enter a command based on the Set-TransportServer or Set-MailboxServer cmdlet. For example, the following command disables message tracking on the Exchange Server 2010 Hub Transport server VAN-EX1:

Set-TransportServer -Identity VAN-EX1 -MessageTrackingLogEnabled:$false

The following command enables message tracking on the Exchange Server 2010 Mailbox server VAN-EX2:

Set-MailboxServer -Identity VAN-EX2 -MessageTrackingLogEnabled:$true

The following command changes the path to the message tracking log on Hub Transport server VAN-EX1 to C:\Logfiles\MessageTracking:

Set-TransportServer -Identity VAN-EX1 -MessageTrackingLogPath C:\LogfilesMessageTracking

The following command changes the path to the message tracking log on Mailbox server VAN-EX2 to C:\Logfiles\Tracking\MessageLogs:

Set-MailboxServer -Identity VAN-EX2 -MessageTrackingLogPath C:\Logfiles\TrackingMessageLogs

Configuring the Size and Age of Message Tracking Log Files

By default, the maximum size for each message tracking log file is 10 megabytes (MB). When a message tracking log file reaches its maximum size, Exchange Server 2010 opens a new message tracking log file. This continues until the message tracking log directory reaches its specified maximum size (by default 250 MB) or until a message tracking log file reaches its specified maximum age (by default 30 days). In either of these cases, Exchange Server 2010 deletes the oldest message tracking log file.

You can use the EMS (but not the EMC) to change the maximum size of each message tracking log file, the maximum age of each message tracking log file, and the maximum size for the entire message tracking log directory on Hub Transport, Edge Transport, and Mailbox servers.

The following command changes the maximum size of each message tracking log file on the Hub Transport server VAN-EX1 to 15MB (the same command would work on an Edge Transport server):

Set-TransportServer -Identity VAN-EX1 -MessageTrackingLogMaxFileSize 15MB

The following command changes the maximum age of each message tracking log file on the Hub Transport server VAN-EX1 to 35 days (as before, the same command would work on an Edge Transport server):

Set-TransportServer -Identity VAN-EX1 -MessageTrackingLogMaxAge 35.00:00:00

The following command changes the maximum size of the message tracking log file directory on the Hub Transport server VAN-EX1 to 300 MB (again the same command would work on an Edge Transport server):

Set-TransportServer -Identity VAN-EX1 -MessageTrackingLogMaxDirectorySize 300MB

The commands to configure maximum log size and age and the maximum size of the message tracking log file directory on a Mailbox server are similar, except that the Set-MailboxServer cmdlet is used. Note that if an Exchange Server 2010 server holds both the Mailbox and the Hub Transport roles, the effective maximum size of its message tracking log file directory is twice the size that is specified because message tracking log files for the mailbox and the transport functions have different prefixes. File prefixes are discussed later in this lesson.

The following command changes the maximum size of each message tracking log file on the Mailbox server VAN-EX2 to 20 MB:

Set-MailboxServer -Identity VAN-EX2 -MessageTrackingLogMaxFileSize 20MB

The following command changes the maximum age of each message tracking log on the Mailbox server VAN-EX2 to 40 days:

Set-MailboxServer -Identity VAN-EX2 -MessageTrackingLogMaxAge 40.00:00:00

The following command changes the maximum size of the message tracking log file directory on the Mailbox server VAN-EX2 to 350 MB:

Set-MailboxServer -Identity VAN-EX2 -MessageTrackingLogMaxDirectorySize 350MB