Special Edition Microsoft Exchange Server 5.5

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Planning Connections to Microsoft Mail Systems



Integration of Microsoft Mail 3.x (PC and AppleTalk) and your Exchange Server is established with the Microsoft Mail Connector, which essentially combines the functions of a Microsoft Mail gateway post office and External Message Transfer Agent. It also provides the connectivity link that ties Exchange gateways, Microsoft Mail 3.x gateways, and other Exchange connectors. The Microsoft Mail Connector allows Exchange Server to route and transfer messages to one or more Microsoft Mail 3.x (PC) systems over LAN, asynchronous, or X.25 connections.

You can configure Microsoft Mail Connector for message transfer and routing by using components provided with Exchange Server. The components built into the Microsoft Mail Connector are comparable to the components in the Microsoft Mail 3.x Post Office and External message transfer programs. The Microsoft Mail Connector comprises a temporary information store and two components that run as services on a Windows NT Server, which allows for better error logging, memory management, and performance monitoring of the entire messaging system. Integration of an existing Microsoft Mail 3.x system, using the External or the Multitasking MTA programs with Exchange Server, can be easily configured to allow a coexistence of the two messaging systems on the same LAN.

Once you establish the message route, you synchronize the Global Address List (GAL) by implementing Exchange as either a directory synchronization requestor to a Microsoft Mail 3.x directory synchronization server, or a directory synchronization server for all Microsoft Mail 3.x directory synchronization requestors. Later in this chapter, I will give you tips on when to migrate a directory synchronization server from Microsoft Mail 3.x to Exchange.

Understanding Microsoft Mail Connector Components

The following three components are located within the Microsoft Mail Connector and work together to transparently transfer and route messages to and from Microsoft Mail Post Offices (see Figure 7.1):

Using Microsoft Mail Connector Interchange

The Microsoft Mail Connector Interchange is a Windows NT service that transfers messages between the Exchange MTA and the Microsoft Mail Connector Post Office. Outbound messages are converted to Mail 3.x format and placed into the Connector Post Office in the same file structure and format that Microsoft Mail queues messages for external post offices. Inbound messages are placed in the Connector Post Office by the Microsoft Mail Connector (PC) MTA, converted to Exchange Interpersonal Messages (IPM), and queued for the Exchange MTA. For proper configuration, make the following choices in the Microsoft Mail Connector Interchange tab:

FIG. 7.1 Microsoft Mail Connector components.

Using Microsoft Mail Connector Post Office

The Microsoft Mail Connector Post Office is a temporary information store for messages. It resembles the file structure of a Microsoft Mail 3.x Post Office. The Microsoft Mail Connector Post Office has enough of the file structure and support files to receive mail in a Microsoft Mail 3.x format from the Connector Interchange or the Microsoft Mail Connector PC MTA. The Connector Post Office is sometimes referred to as a gateway Post Office or shadow Post Office because it is dedicated to message transfer and has no local mailboxes.

Using Microsoft Mail Connector (PC) MTA (Message Transfer Agent)

The Microsoft Mail Connector (PC) MTA is a Windows NT service that connects to and transfers mail between the Microsoft Mail Connector Post Office and one or more Microsoft Mail (PC) Post Offices. It can execute most of the same operations as the Microsoft Mail 3.x External and Multitasking MTA programs, including message distribution and delivery to users on Microsoft Mail Post Offices. The MTA contains the information for which the direct and indirect connection routing of mail messages occurs between Microsoft Mail 3.x Post Offices. The information is read from a list that is configured through the Microsoft Mail Connector section of the Administrator program. The Microsoft Mail Connector PC MTA is configured for LAN, asynchronous, and X.25 transport connections.

Once again, all of the Connector's components can be configured in the Administrator program, under the Microsoft Mail Connector, on the individual component's tab.

In a Microsoft Mail 3.x environment, the External mail transfer agent (MTA) and the Multitasking MTA (MMTA) programs transfer and route messages between Microsoft Mail Post Offices. Because the Microsoft Mail Connector PC MTA emulates the message routing ability of the Microsoft Mail External and MMTA, you can replace your existing instances of those programs and services with the Microsoft Mail Connector PC MTA. The Microsoft Mail Connector PC MTA does not completely handle all of the functions of the Microsoft Mail 3.x External or Multitasking MTA. In some cases, the messaging system may still require some of the functions found in the External program.

For example, when Microsoft Mail 3.x remote users dial in for their messages, they dial into the Microsoft Mail MTA (External), which handles message transfer between remote users and the Microsoft Mail 3.x Post Offices. Because some users still use the Microsoft Mail Remote client program, the Microsoft Mail Connector PC MTA cannot replace the Microsoft Mail MTA (External). The continued use of the External program, as well as the Microsoft Mail Connector, must be maintained.

When both Exchange and Microsoft Mail 3.x Post Offices reside on the same LAN, you can configure the Microsoft Mail Connector to transfer route messages from the Exchange Server MTA, convert the message, and deliver the message to the correct recipient on the Microsoft Mail 3.x Post Office.

When you send a message to an Exchange Server destined for a Microsoft Mail 3.x recipient located on the same LAN, the message is received by the Exchange MTA. Then the message is routed by the Exchange MTA to the Microsoft Mail Connector Interchange, where the message and any OLE attachments are converted to Microsoft Mail 3.x format. The converted message is then sent to the Microsoft Mail Connector Post Office (Information Store), where it is held until the Microsoft Mail Connector MTA picks it up and delivers it to the appropriate Microsoft Mail 3.x Post Office (see Figure 7.2).

FIG. 7.2 The message transfer process from Exchange Server MTA to Microsoft Mail 3.x.

The Microsoft Mail Connector, External MTA, and Multitasking MTA determine their routing information between Exchange Server and Microsoft Mail 3.x by the information that is entered into the Address Space. The address space is defined as a set of Microsoft Mail 3.x Post Office names to which the Microsoft Mail Connector will rout mail messages. This entry in the address space is also known as an Instance.

When connecting Microsoft Mail 3.x over X.25 or asynchronous services, you have to configure the External MTA or Multitasking MTA program at the Remote Post Office location with an instance in the address space of the MTA to connect with the Microsoft Mail Connector (see Figure 7.3).

FIG. 7.3 Basic Microsoft Mail 3.x External (or Multitasking MTA) layout.

Configuring Connections to Existing Post Offices

When planning your Exchange integration with Microsoft Mail, it is important to understand your Microsoft Mail 3.x infrastructure. The Microsoft Mail 3.x infrastructure comprises network topologies and message routes. The network topology includes LAN, asynchronous, and X.25. The message routes are either direct connections between two post offices or an indirect connection via another Microsoft Mail 3.x Post Office.

Configuring LAN Connections to Existing Post Offices

The LAN connection happens to be the easiest and one of the simplest types of connections in terms of setup and administration. In this particular case, you don't have to use the External or Multitasking MTA programs at all. Instead, you can use the Administrator program in Exchange Server to configure the majority of the message routing and transfer between the Microsoft Mail Connector and the Microsoft Mail 3.x Post Offices. You can learn more about the Exchange Administration program in Chapter 12, "Using the Administrator Program."

Asynchronous and X.25 Connections for Remote Post Offices

You need two components to connect Exchange Server and a Microsoft Mail 3.x Post Office over an X.25 or asynchronous service. The first is the Microsoft Mail Connector PC MTA. The second is the Microsoft Mail 3.x External or Multitasking MTA program provided with Microsoft Mail 3.x Server. This program provides the message transfer and modem management functions necessary to communicate over a remote connection within a Microsoft Mail 3.x system. If the Microsoft Mail 3.x External MTA will reside on a DOS computer, this needs to be a dedicated computer. DOS does not allow multiple sessions, or executables, to occur at the same time.

Setting up the Multitasking MTA on a Windows NT Workstation allows multiple MTAs to reside and route messages on a single computer. The Multitasking MTA can also reside on a separate Windows NT Server if desired. I recommend using the Windows NT Workstation because it doesn't require passwords.

If a direct asynchronous or X.25 route is desired, Microsoft Mail 3.x External or Multitasking MTA must be located on the same LAN as the remote Post Office (refer to Figure 7.3).

Direct and Indirect Message Routes

As with Microsoft Mail 3.x, message routes from Exchange to Microsoft Mail 3.x can be direct or indirect.

If you have multiple Microsoft Mail 3.x Post Offices on the same LAN, one way to increase the performance of the Exchange Server is to configure a direct connection from Exchange to a Microsoft Mail 3.x Post Office. Configure the remaining Microsoft Mail Post Offices Indirect via the Direct Microsoft Mail 3.x Post Office. Once the single direct message route is established, the Exchange Server has a message route to all Microsoft Mail Post Offices as long as the Exchange infrastructure is properly configured. Performance of the Exchange Server is enhanced because the Microsoft Mail Connector PC MTA forwards and receives mail from only one Microsoft Mail 3.x Post Office. Therefore, the Exchange Server will not have to make network connections to the other Microsoft Mail 3.x Post Offices to deliver or receive mail. This configuration also reduces the complexity of the integration if the indirect post offices need asynchronous or X.25 connections to directly connect to Exchange.

As I mentioned before, it is important that you understand the Microsoft Mail 3.x infrastructure. If it is stable, you can leverage it instead of replacing it with Exchange Components (see Figure 7.4).

Microsoft Mail Connector has an integrated feature that automatically extracts indirect routing information from a Microsoft Mail 3.x Post Office. This feature eliminates the need to manually configure the routing information for each of the Microsoft Mail 3.x Post Offices connected indirectly to the Microsoft Mail Connector. The only requirement for the automatic upload of routing information is a LAN connection. Unfortunately, if the Microsoft Mail 3.x Post Office you are trying to connect to is over an asynchronous or X.25 service, the indirect routing information will have to be entered manually on the Microsoft Mail Connector Properties sheet.

FIG. 7.4 Basic LAN connection with direct and indirect route configuration.


CAUTION: Use this feature with caution, I have seen invalid message routes uploaded into Exchange, which caused circular routing errors.

Optimizing the Exchange and Microsoft Mail Integration

You can optimize your Exchange and Microsoft Mail integration by adding additional Microsoft Mail PC MTAs and Microsoft Mail Connectors. Furthermore, Microsoft Mail 3.x can use Exchange's more robust infrastructure to transfer messages between Microsoft Mail 3.x Post Offices.

Using Multiple Microsoft Mail Connector (PC) MTAs

Each Microsoft Mail MTA instance will react differently depending on the type of connection it uses.


NOTE: Each instance is named and registered as a Windows NT service on the Exchange Server computer on which it was created, and it can be started or stopped independently of any other service.

Each instance has a primary connection type, although all instances can service LAN- connected Post Offices. Depending on the number of Post Offices and their connection types, it might be more efficient to group the same connection types in the same instance. If the connection types are diverse, multiple instances should be created.

For example, if your network contains ten LAN-connected Microsoft Mail 3.x Post Offices and five asynchronous-connected Microsoft Mail 3.x Post Offices, it would be more efficient to create one instance on the Microsoft Mail Connector MTA for servicing only the LAN- connected Post Offices and another instance for connecting to and servicing the asynchron ous Post Offices.

Using Multiple Microsoft Mail Connectors

If your organization contains a large number of Microsoft Mail 3.x Post Offices, you might need multiple Microsoft Mail Connector MTAs for message connectivity between Microsoft Mail 3.x and Exchange recipients. Because every Exchange Server uses the same Microsoft Mail e-mail address in the site, Microsoft Mail essentially views each of the Exchange sites as one large Microsoft Mail Post Office. Therefore, it is recommended for routing purposes, that one Microsoft Mail Connector MTA should be used for every Exchange Server site. If your Exchange Server Organization has multiple Exchange sites and a large number of Microsoft Mail Post Offices, the post offices can be grouped into clusters much like an Exchange site. Configure each Exchange site with at least one Microsoft Mail Connector with only the address spaces of the Microsoft Mail Post Offices adjacent to the site (such as on the same LAN). Directory replication between Exchange sites makes the other sites aware of the connection to Microsoft Mail.

If you are going to use multiple Microsoft Mail Connectors, make sure each Exchange Server has its own Microsoft Mail Connector MTA. Also, you can use duplicate address entries in two or more Microsoft Mail Connectors to route messages based on cost. This is useful for redundancy and for load balancing of traffic across connections and between servers.

Using Exchange Server as a Backbone to Microsoft Mail (PC)

Because Exchange provides a more robust and stable infrastructure, you may consider replacing your existing Microsoft Mail infrastructure with an Exchange backbone. Using an Exchange Organization as a backbone enables Microsoft Mail Post Office to Post Office traffic to use Exchange messaging components such as site connectors.

To backbone Microsoft Mail over Exchange, verify the following things:

FIG. 7.5 Basic site-to-site backbone configuration.

Using Existing Microsoft Mail (PC) Gateways

Exchange Server supports a wide variety of Microsoft Mail (PC) gateways, which grant messaging services to other messaging systems. Supported Microsoft Mail (PC) gateways include the following:

All of these gateway programs come with Microsoft Mail Server 3.x on an options disk included with the software. Each of the gateway programs requires a short installation and configuration process. They are menu driven and easy to follow.

There are two ways Exchange clients can pass information through an existing Microsoft Mail 3.x mail system gateway. First, a typical gateway scenario in an existing Microsoft Mail 3.x environment has the Microsoft Mail 3.x gateway software running on a dedicated computer. A Microsoft Mail 3.x Post Office needs to be selected as the gateway Post Office. All messages destined for the foreign mail system will pass through this gateway Post Office, and vice versa. In order for Exchange clients to access the actual gateway and pass messages to the foreign mail system, the Exchange Connector Post Office must have the Microsoft Mail 3.x gateway access component installed (see Figure 7.6). Second, if an Exchange Server is selected as the gateway Post Office, the Microsoft Mail 3.x Post Offices must have a gateway access component. Either way enables integration of an Exchange Server into an existing Microsoft Mail 3.x gateway scenario (see Figure 7.7).

FIG. 7.6 Basic Microsoft Mail 3.x gateway layout.

FIG. 7.7 A typical gateway scenario.

Using Exchange Connectors as Gateways

If you decide to use Exchange for your gateway needs, you can use the Exchange X.400 Connector or the Internet Mail Service as gateways to foreign systems. The Microsoft Mail 3.x Post Office that is given access to the foreign mail service must be connected to the Exchange Server via the Microsoft Mail Connector and must have a gateway access component installed on it. One benefit of using Exchange as a gateway is that you don't have to have a dedicated computer running the gateway (see Figure 7.8).

When a mail message is sent from a Microsoft Mail 3.x Post Office destined for the foreign mail service, the message is sent to the Microsoft Mail Connector, which passes it to either the Exchange X.400 Connector or the Internet Mail Connector. The selected connector then passes the message to the foreign mail service. The process is reversed for a message traveling from a foreign mail system to a Microsoft Mail 3.x Post Office.

Figure 7.8 illustrates another method of using Exchange as a gateway.

FIG. 7.8 Using Exchange as a gateway.

The Connector for cc:Mail and the Connector for Lotus Notes can also be used by Microsoft Mail clients that don't have gateway access components installed on the Microsoft Mail Post Offices. This is possible if directory synchronization between cc:Mail/Lotus Notes has been established and if the Microsoft Mail Directory Synchronization Agent is configured to export custom recipients to Microsoft Mail Global Address Books (GAL). When directory synchronization occurs between Exchange and Microsoft Mail, custom recipients of Microsoft Mail proxy addresses are synchronized with the Microsoft Mail 3.x address book. Therefore, a message composed to the cc:Mail/Lotus Notes user from Microsoft Mail will be sent to Exchange through the Microsoft Mail Connector because it has the appropriate network and post office address from the Exchange Server Microsoft Mail proxy generator. The Exchange MTA then queues the message with the appropriate connector, based on the type of custom recipient.

Directory Replication and Synchronization

It is important that you understand the difference between Exchange directory replication and directory synchronization.

Directory replication is the automatic process of updating the directories between Exchange Server and Exchange Server sites. The replicated information includes all the information available about an organization's resources and users, including mailboxes, public folders, distribution lists, servers, and more. Other components use the directory to map addresses and route messages. Replication can also be configured to automatically replicate all directory information or only the desired amount of the directory information between multiple Exchange sites.

Directory synchronization is the process of synchronizing an Exchange global address directory with post office addresses from Microsoft Mail (PC) and Microsoft Mail (AppleTalk) systems. To do this, you use the Microsoft Mail 3.x DISPATCH program included with the Microsoft Mail 3.x Server. As in directory replication between Exchange Server sites, during synchronization, only the desired information is transferred using trust levels.

In order for an Exchange Server to accomplish directory synchronization with a Microsoft Mail 3.x mail system, the Exchange Server must be running the Microsoft Mail 3.x Directory Synchronization Agent. The Directory Synchronization Agent on an Exchange Server plays one of two roles depending on the mail system environment: DIRSYNC Server or DIRSYNC Requester (see Figure 7.9). On an existing Microsoft Mail 3.x system, the Exchange server can be configured as either a DIRSYNC Server or Requestor (see Figure 7.10). However, the Exchange Server cannot be configured as both a Server and a Requestor simultaneously. On a Microsoft Mail 3.x mail system, there can be only one DIRSYNC Server. All of the rest of the Microsoft Mail 3.x Post Offices can be configured as DIRSYNC Requestors.

If the Exchange Server is configured as the DIRSYNC Server, it can synchronize all other Microsoft Mail 3.x Post Offices set up as DIRSYNC Requestors.

You may be tempted to migrate your directory synchronization server to Exchange Server if you are having trouble maintaining your Global Address List (GAL) on Microsoft Mail. Before migrating the directory server, it is important to understand which cycle is failing on the Microsoft Mail Directory Synchronization Protocol. The Microsoft Mail Directory Synchronization Protocol comprises three schedule events:

Time 1 (T1) is when updates are sent from directory synchronization requestors. All post offices are required to send address book updates to the directory synchronization server.

Time 2 (T2) is when the directory synchronization server takes all the updates from the requestors and processes a master transaction list that is sent back to the directory requestors.

Time 3 (T3) is when the requestors update their Global Address Lists from the update sent from the directory synchronization server.

Usually the cycle that fails on Microsoft Mail is the T3 cycle, which prohibits a proper rebuild of the Global Address List (GAL) on that Microsoft Mail Post Office, giving the impression that the directory server is not performing the T2 cycle. Migrating the directory synchronization server from Microsoft Mail to Exchange only migrates the T2 cycle, which is usually stable on Microsoft Mail. I generally do not move the directory synchronization server to Exchange unless it is necessary to decommission the Microsoft Mail Post Office that is the directory synchronization server.

FIG. 7.9 Using Exchange as a DIRSYNC Server on an existing Microsoft Mail system.

FIG. 7.10 Using Exchange as a DIRSYNC Requestor on an existing Microsoft Mail system.


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