Copyright ©1996, Que Corporation. All rights reserved. No part of this book may be used or reproduced in any form or by any means, or stored in a database or retrieval system without prior written permission of the publisher except in the case of brief quotations embodied in critical articles and reviews. Making copies of any part of this book for any purpose other than your own personal use is a violation of United States copyright laws. For information, address Que Corporation, 201 West 103rd Street, Indianapolis, IN 46290 or at support@mcp .com.

Notice: This material is excerpted from Special Edition Using Microsoft Exchange Server, ISBN: 0-7897-0687-3. The electronic version of this material has not been through the final proof reading stage that the book goes through before being published in printed form. Some errors may exist here that are corrected before the book is published. This material is provided "as is" without any warranty of any kind.

Chapter 13 - Message Transfer Configuration

The Microsoft Exchange Message Transfer Agent (MTA) is the key component that provides addressing and routing information and that delivers messages. Proper configuration of MTA settings is important to an efficient Exchange organization. As described in Chapter 3, "Exchange's Integrated Server Components," a message that originates in an Exchange mailbox reaches its destination in only two ways:

Unless your organization consists primarily of one or two Exchange servers, the MTAs on various levels are the entities that are responsible for message routing and transmission.

In this chapter, you learn the following:

Stephen

Understanding the Transfer Agent Components

The Microsoft Exchange Message Transfer Agent is primarily a Windows NT service running on each Exchange server in your organization. For connection to Microsoft Mail systems, an additional service called the MS Mail Connector (PC) MTA negotiates message transmission with MS Mail for PC networks.

Configuration of the primary Exchange MTA is handled though two sets of property pages:

Let's discuss some of the essential parameters involved in performing MTA Site Configuration.

Dead Letter

Any message that is defined as undeliverable by the Message Transfer Agent is classified as a dead letter. You can specify a dead-letter recipient (usually, an administrator) from within the MTA site configuration property pages.

Message Tracking

To keep record of Message Transfer Agent activity within a Microsoft Exchange site, enable message tracking. A daily log file is generated and stored in the EXCHSRVR\TRACKING.LOG directory. Message tracking log files are in a text format. The full file name, to use the example would be : EXCHSRVR\TRACKING\960529.LOG. The individual log files are:

Message Queues

Each server has a list of messages that are waiting to be delivered by its MTA. The queues are distinguished as being either private or public Information Store messages. Messages are held in the queue until the MTA can successfully establish a connection with a remote MTA and transfer the messages or until the messages exceed their lifetimes (set in the messaging defaults).

Messaging Defaults

Settings for how (and how long) to transfer a message before certain time-outs occurs are called messaging defaults. These values are set in the MTA Site Configuration properties and are used by all MTAs in the site unless a specific connection uses MTA override parameters.

MTA Overrides

Certain connectors—namely, the Dynamic RAS Connector and the X.400 connector—provide for object-specific MTA settings. Use the Override property page to change the default Microsoft Exchange Server MTA attributes when using a specific X.400 or dynamic RAS connector. Keep in mind their existence when you define messaging defaults in the MTA Site Configuration property page. Override propertypages are there for developing flexibility in MTA configuration.

Performing MTA Site Configuration

To open the MTA Site Configuration property pages, follow these steps:

1. Navigate to your desired site with the Exchange Administrator program.

2. Click the Configuration container of the selected site (see fig. 13.1). All the site-configuration objects appear in the Administrator program's right window.

Fig. 13.1

The MTA Site Configuration is located in the Configuration container.

3. Select the MTA Site Configuration object from the list.

4. Open the MTA Site Configuration Object property pages by double-clicking on the object.

At this point, you have three property pages to configure:

The General Tab

To configure the General features, such as display name of the MTA Site Configuration Object, follow these steps:

1. Click the General tab of the MTA Site Configuration property pages (see fig. 13.2).

Fig. 13.2

The General MTA site configuration property page.

2. Type a new name in the Display Name box, if you want. The default name is MTA Site Configuration.

By default, the Directory Name, Sire-MTA-Config, cannot be changed.

1. In the Dead Letter Recipient section, click the None radio button if you want all nondeliverable messages to be deleted. By default, this option is selected.

2. Click the Modify button if you want to enter or change a name in the Dead Letter Recipient text box. The Exchange address list appears. Click the radio button next to the name in the box to designate that recipient as the dead-letter recipient.

3. Click the Enable Message Tracking check box to instruct the System Attendant to keep a daily log ofall messages processed by the MTA. This check box corresponds to the "Enable Message Tracking" check box in the Information Store Site Configuration property page.

4. Click Apply to set these properties and continue with viewing/changing of other properties.

5. When you finish making settings, click OK to return to the Administrator program.

The Permissions Tab

This property page allows you to define certain Windows NT user accounts that have rights to modify this directory object. See chapter 11, "Using the Administrator Program," for a detailed description on working with the standard Permissions property page.

The Messaging Defaults Tab

To set the messaging default values for the MTA Site Configuration object, follow these steps:

1. Click the Messaging Defaults tab of the MTA Site Configuration property pages (see fig. 13.3).

Fig. 13.3

Messaging defaults govern each connection made by the MTA.

To return to the default Message Transfer Agent settings, click the Reset Default Values button.

2. Enter specific MTA configuration variables, as described in Table 13.1, which follows these steps.

3. To the right of each item listed in the table is a box that contains a default numeric value. Replace any value with a number that will be used in establishing a connection through any MTA in the current site.

4. Click Apply to set these properties and continue with other properties.

4. When you finish making settings, click OK to return to the Administrator program.

Table 13.1

MTA Site Configuration Parameter Values

Variable Description

RTS Values

Checkpoint Size (K) The value (in kilobytes) used to verify packet transmission with returned checkpoints. By default, this value is 30.
Recovery Timeout (Sec) The time delay (in seconds) before a broken transmission is retried. By default, the delay is 60 seconds.
Window Size The number of checkpoints (in kilobytes) that can be transmitted without acknowledgment. By default, this value is 5.

Connection Retry Values

Max Open Retries The maximum number of consecutive failed attempts before the MTA ceases trying to open a communication channel with a remote MTA. By default, an MTA makes 144 attempts.
Max Transfer Retries The maximum number of consecutive failed attempts before the MTA ceases trying to transfer a message packet. By default, the MTA makes 2 attempts.
Open Interval (Sec) The delay (in seconds) between attempts to open a communication channel. By default, the delay is 600 seconds.

If you combine the default 144 Max Open Retries with the default 600-second Open Interval, Exchange waits 24 hours before returning a message as undeliverable.

Transfer Interval (Sec) The delay (in seconds) between attempts to retransmit a failed message packet. By default, this delay is 120 seconds.

Association Parameters

Lifetime (Sec) The maximum time that an idle connection between MTAs remains open. By default, an idle link is held open for 300 seconds after the last communication.
Disconnect (Sec) The maximum time allowed for establishing or terminating a connection before the session is ended independently. By default, this time is 120 seconds.
Threshold (Msgs) The number of messages that must be queued at this MTA before the MTA initiates a link to a remote MTA. By default, 50 messages must be awaiting transmission.

Transfer Timeouts (Sec/K)

Urgent The delay (in seconds per kilobyte of total message size) between retries of urgent messages. By default, this delay is 1,000 seconds.
Normal The delay (in seconds per kilobyte of total message size) between retries of normal messages. By default, this delay is 2,000 seconds
Non-Urgent The delay (in seconds per kilobyte of total message size) between retries of nonurgent messages. By default, this delay is 3,000 seconds.

The following section discusses configuring Message Transfer Agent properties for each Microsoft Exchange Server.

Configuring Local MTA Properties

Each Microsoft Exchange Server has a Message Transfer Agent. The MTA property pages are designed to configure and manage this service.

First, you must select the MTA from the server within your site. Follow these steps:

1. Navigate to your desired site with the Exchange Administrator program.

2. Click the Configuration container of the selected site. All the site-configuration objects appear in the Administrator program's right window.

3. Open the Servers container by double-clicking on it. A list of Exchange servers in your site appears.

4. Click the name of the server that houses the MTA that you want to configure (see fig. 13.4). The following list of server objects is visible on the right display window of the Microsoft Exchange Administrator program.

Fig. 13.4

The Message Transfer Agent directory object is located inside the server container.

1. Click the Message Transfer Agent object, and open its property pages.

The following three property pages become available for you to configure:

The General Tab

To set values for the local MTA name, password, and other general message transfer preferences for this server, follow these steps:

1. Click the General tab of the message transfer agent property pages (see fig. 13.5).

Fig. 13.5

The General Message Transfer Agent property page.

1. Type a name in the Local MTA Name box. This name will be used by remote MTAs (either on remote Exchange servers or foreign messaging systems) to identify this MTA. By default, this name is the name of the Exchange server on which the MTA is installed.

2. Type a password in the Local MTA Password box, if necessary. If you enter a password in this box, any remote MTA (either on remote Exchange servers or foreign messaging systems) must be configured to provide this password for authentication. By default, this box is blank, and no authentication is required of the remote MTA.

If you decide to change the Local MTA Name or to add or change the Local MTA Password, be sure to take into consideration any previously established MTA connections. All remote sites (and foreign systems, such as X.400) must be adjusted to reflect the new information. Authentication is never required between two MTAs in the same site.

Use these settings as a filter to manage the messaging load for all traffic to and from this server. The upper-limit settings have precedence over message-size settings in individual connectors and recipient objects.

3. In the Message Size section, click the radio button that indicates how you want to restrict the passage of messages through this message transfer agent.

4. Click the No Limit radio button to allow this MTA to deliver messages of any size.

5. If you want to set a size limit, click the Maximum (K) radio button; then, in the text box, type an upper limit (in kilobytes) for messages that travel through this MTA. Any message that exceeds this size limit will be returned as undeliverable.

Rebuilding routing tables sometimes takes several minutes, so it is a good idea to go through each MTA property sheet, make all changes, and then recalculate routing.

6. Click the Recalculate Routing button to rebuild the routing tables for this MTA. (See chapter 2, "Understanding Exchange's Organization and Sites," for more information on routing tables.) New routing information for this MTA will propagate to all Exchange servers within the site automatically.

Routing tables are rebuilt once a day automatically.

7. Click the Expand Remote Distribution Lists Locally check box to force distribution lists created on remote sites to be expanded on this server. When a message is sent to a distribution list by a user on this server, the message is split into its component recipients locally. If this box is not checked, the distribution list is expanded in the remote site, following the configuration in the distribution list's own property pages. By default, this box is checked, and distribution lists are expanded locally.

Consider both the physical locations of the majority of the distribution list's recipients and the messaging load on the local server. If you choose the default settings, make certain that the local server can handle the extra messaging traffic; expanding large distribution lists can be a considerable load on an already overburdened Exchange server. Also, if you know that the majority of the distribution list's recipients reside on Exchange servers on the remote site, consider allowing the list to be expanded there.

8. Click the Convert Incoming Messages to MS Exchange Contents check box to convert all messages to Exchange's MAPI-compliant format automatically. By default, this option is not selected, and messages are kept in the format in which they arrive at the MTA (such as standard X.400 format).

9. If you want, make an entry in the Administrative Note text box.

10. Click Apply to set these properties and continue with other properties.

11. When you finish making settings, click OK to return to the Administrator program.

The QueuesTab

The Queues tab of the message transfer agent property pages lists messages that are awaiting delivery by the MTA. The two primary windows are Queue Name, which shows the queue that you are currently viewing, and Message List, which displays the messages in that queue. From the Message List window, you can view details about a specific message in the queue, change its priority for delivery, or delete it.

The Message List window has three columns that contain information about a particular message:

To configure the Queues property page, follow these steps:

1. Click the Queues tab from the message transfer agent property pages (see fig. 13.6).

Fig. 13.6

Messages waiting to be delivered are held in the queue.

2. From the Queue Name drop-down list, select the message queue to display. The list shows queues for the private and public information stores, as well as for any installed gateways.

The Internet Mail connector and Microsoft Mail connector have separate queues that you can access through their property pages.

3. Select a message, and click Details to view additional information about it.

4. The additional message information includes the message originator, submit time, message size, and priority. This button is dimmed if no messages are in the queue.

5. Click the Refresh button to update the Message List window with the latest list of messages in the MTA queue.

6. Click Priority to display the message's priority, and change the priority of the message, if you want. Priority can be low, medium, or high. Messages are sent in order of priority. A message's priority is set when a message is created.

7. To remove a message from the MTA queue, select a message and then click Delete.

8. Click Apply to set these properties and continue with other properties.

9. When you finish making settings, click OK to return to the Administrator program.

The Diagnostic Logging Tab

This property page works in conjunction with the Windows NT Event Log to record various "events" that occur within the message transfer agent. Various levels of logging determine what constitutes an event and, therefore, what types of information are actually recorded. For troubleshooting purposes, you would want a very detailed record of occurrences within the MTA; hence, you would set a high logging level. Normally, however, you want to log only critical events, so set a lower logging level for everyday operation.

From Here...

The Message transfer agent is the key component for routing and delivering messages to their destination. You administrate MTA functions through two main sets of property pages:

1. MTA Site Configuration Settings for an entire Exchange site

2. Message Transfer Agent Settings for an individual Exchange server's MTA service.

See the following chapters for more information on topics related to the MTA.

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