Anytime you’re rolling out an Exchange 2000 implementation, one of the biggest questions you have to ask yourself is how the clients will access their mailboxes, calendars, public folders, and other Exchange Server-based resources. In an environment in which all the clients and Exchange servers are in the same building, it’s almost always okay to use Outlook 2000 as your client software. One of the few exceptions to this would be a situation in which the client PCs lacked sufficient hardware or software to run Outlook 2000. While supporting a local office is easy, the real trick is supporting branch offices. Choosing a client for a branch office is much more complex than simply picking out client software for your local office. In this Daily Drill Down, I’ll discuss the issues you need to consider when configuring Exchange clients in branch offices.

What’s to think about?
If you’ve ever supported a local office, you may be wondering what’s to think about when setting up client access at a remote office. Why not just install Outlook 2000 and get on with life? Well, the truth is that Outlook 2000 might not always be the best choice for every situation. For example, your client machines might be incapable of running Outlook 2000 because of limited hardware or because of an outdated operating system. Likewise, your organization might not have sufficient money in the budget to purchase enough copies of Outlook 2000 to go around.

Of course, these all seem like obvious reasons for not using Outlook 2000, but there are other reasons that are just as important. Choosing a messaging client is a big decision, and it’s important to weigh all of the choices carefully to see which client software package will coexist the most peacefully with your existing network infrastructure. For example, you don’t want to use a client that’s going to consume all of your network’s bandwidth. Likewise, if security is a big concern in your organization, you’ll want to use a client that doesn’t compromise the security you’ve worked so hard to establish.

Messaging client software and bandwidth
Before I get into a discussion of the various messaging clients available to you, I want to discuss the bandwidth concerns you’ll have to deal with. As you probably know, bandwidth refers to the amount of traffic your network can carry. In this Daily Drill Down, I’m discussing a situation in which the Exchange clients are located in a different facility from the servers. Many times, buildings—whether across town or across an ocean—are linked to one another by a slower connection than that used within the buildings.

If your clients are located in a remote office but all of your Exchange servers are located in the local office, then all of the client access traffic will have to pass through the slow WAN link that connects the buildings. This is called centralized Exchange administration. For the purposes of this Daily Drill Down, I’m assuming this is the way your organization is configured. You can get around many of the bandwidth problems by implementing distributed administration.

Distributed administration basically involves having Exchange servers at the remote offices. By doing so, you can keep interoffice mail from ever having to flow across the WAN link. Only traffic that’s destined for a mailbox in the other office will flow across the link.

Of course, many hybrid Exchange implementations use a combination of centralized and distributed administration. However, the physical architecture of an Exchange organization is beyond the scope of this Daily Drill Down. I simply want to point out that all of the client descriptions in this Daily Drill Down involving bandwidth assume the client is accessing an Exchange server from across a WAN link. I also want to make you realize that if bandwidth is your only reason for not using a particular client package, there’s a way to get around the bandwidth issue. With that said, let’s begin looking at the various clients available to you.

Outlook 2000
If your organization has plenty of bandwidth to spare, Outlook 2000 is often the best choice for accessing an Exchange server. So what makes Outlook 2000 so great? Three words: features, features, features.

Outlook 2000 is designed to take advantage of every feature Exchange 2000 has to offer. For example, Outlook 2000 supports the use of some of the less common features that other types of clients don’t support, such as the free/busy information, inbox rules, and the ability to work off-line. Outlook 2000 also has many other useful features, such as a spell checker and the ability to perform a variety of searches.

There are actually dozens of advantages to using Outlook 2000. For example, Outlook 2000 is designed to perform a lot of the necessary processing locally. This means that Outlook won’t bog down your servers with client-related message processing. Outlook 2000 also offers such features as a journal, notes, and sticky notes. These features aren’t available in any of the other client software packages except for the terminal server client.

Outlook 2000 is also designed to integrate tightly with your existing software, such as Windows and Microsoft Office. In addition, Outlook 2000 can support most of the security features you might have implemented, such as S/MIME (Secure/Multipurpose Internet Mail Extensions) encryption and signing. Outlook also supports digital certificates.

Unfortunately, there are some downsides to using Outlook 2000. For starters, Outlook 2000 is very bandwidth intensive. Outlook 2000 also relies on being able to use several TCP/IP ports. This means you must leave these ports open on your firewall if clients will be using Outlook 2000 from outside your primary network. Another disadvantage is that, as I mentioned earlier, all of the features Outlook 2000 supports come at a price. For example, Outlook 2000 consumes a considerable amount of hard disk space on each client. Likewise, the client PCs must be running Windows 9x, Windows NT, or Windows 2000. The wide variety of features supported by Outlook 2000 can also be confusing to your users. Although Outlook has been designed to be easy to use, it can require an extensive amount of training for your users.

Perhaps the biggest disadvantage to using Outlook is that you have to manage it. For instance, you must keep tabs on how many Outlook licenses you’re using. Likewise, you must reconfigure Outlook each time an employee quits or a new employee is hired.

IMAP4 and POP3
Another method that clients can use to access an Exchange server is through the use of POP3 or IMAP4. Both of these protocols allow clients to access their mailboxes from across the Internet. POP3 is the more common of the two protocols. POP3 allows users to dial up to the Internet, download their messages to their local machine, and then disconnect from the Internet.

In a POP3 environment, all of the messages are ultimately stored on the client machine. A user can compose and read messages while off-line. When the user connects to the Exchange server, any messages the user composed while off-line will be sent and any new messages will be downloaded to the user’s local hard disk.

The advantage of using POP3 is that POP3 is extremely easy to configure. POP3 can also save your company a fortune on your phone bills because it allows users to work off-line most of the time. POP3 also requires minimal bandwidth. A simple modem connection usually works just fine. Another big advantage is that POP3 is a widely used protocol. This means that most firewall packages are configured by default to allow POP3 traffic to pass through the firewall.

Using POP3 has some disadvantages, though. Because POP3 is such a simple protocol, it has limited capabilities. For example, the only Exchange Server folder that it’s capable of accessing is the user’s inbox. Likewise, unless you were to use a rich POP3 client (such as Outlook 2000), a POP3 client is incapable of using any of the other Exchange 2000 features, such as collaboration. One of the biggest disadvantages is that POP3 makes users store their messages locally. This means if a user deletes a message, there’s no getting it back. It also makes the message backup process the user’s responsibility.

IMAP4 works similarly except that all messages are stored on the server. Any time users read or compose a new message, they are interacting directly with the server. IMAP4 offers minimal support for working off-line, and it tends to be more robust than POP3. IMAP4 allows clients to see the entire Exchange server’s folder structure, including public folders. However, like POP3, IMAP4 doesn’t support the other Exchange 2000 features, such as the Calendar. IMAP4 also doesn’t support such functions as collaboration unless you use a rich client.

Terminal services
Another method of accessing an Exchange 2000 server is through a terminal server client. A terminal server allows the Outlook 2000 software to run on a Windows 2000 server. The client simply sees the output of the session. This is similar to running a program remotely through PC Anywhere.

The big advantage to using a terminal server session is that just about any client, including Windows CE, can run a full-blown Outlook 2000 session. Clients are also protected with all of the security found in Windows 2000. Another advantage is that because all of the software runs on the server, any upgrades can simply be applied to the server. You won’t have to worry about upgrading every machine.

Unfortunately, running a terminal server can be expensive. Not only do you have to get a client license for each client that’s accessing the terminal server, but terminal servers require some high-end hardware. That’s because all of the client software is actually running on the server, and therefore the server must be powerful enough to run all the necessary software simultaneously. Likewise, because screen captures are being continuously passed to the end user, terminal servers can be extremely bandwidth intensive. If you’re lacking in bandwidth, the terminal server experience can be painfully slow for your users.

Outlook Web Access
One final way that users can access an Exchange server is through the Web via an Outlook Web client. An Outlook Web client is a Web page that’s generated by Exchange 2000. This Web page is designed to look like an Outlook 2000 session. You can see an example of an Outlook Web client in Figure A.

Figure A
An Outlook Web client is a Web page that’s designed to look like Outlook 2000.

Using an Outlook Web client has many advantages. For starters, your users can access their e-mail from anywhere without any special software outside a standard Web browser. When clients log on through a Web browser, they can access many of the more common Exchange 2000 features, such as their inbox and their calendar. They can also access their appointments, contact information, and any public folders they have access to.

Using an Outlook Web client is good for the administrator, too. One reason for this is that you don’t have to worry about software on the client machine. All upgrades are put in place at the server, so you never have to go reconfigure or upgrade all the client computers. Likewise, as long as a computer has access to the Internet, it can use the Access Web client. Therefore, you can save a lot of money if you were considering upgrading your machines to allow them to run Outlook 2000. It also means that because all the action takes place at the server, the clients require minimal bandwidth.

There are a few disadvantages to the Outlook Web client, though. For example, the Outlook Web client may appear differently depending on which Web browser a client is using. Other disadvantages include the fact that the Outlook Web client is still lacking a few of Outlook 2000’s more advanced features. The Outlook Web client also doesn’t provide a method of working off-line. For more information about Outlook Web Access in Exchange 2000, see the Daily Drill Down titled “Understanding Exchange 2000 Server’s Outlook Web Access.”

In this Daily Drill Down, I’ve explained that you must carefully weigh your options for client software when rolling out Exchange Server to a branch office. As I did, I examined the situations in which it’s appropriate to use each type of client. I also described the pros and cons associated with the various types of Exchange clients.
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