Microsoft Exchange Server 2007: Tony Redmond's Guide to Successful Implementation

581

7

Clients

My first email client was VAXmail (later VMSmail), a character-based cli-

ent that was a part of the VAX/VMS operating system when I first begin

working with it in the early 1980s. VAXmail was simple and straightfor-

ward and got messages through. In fact, you always knew that VAXmail

had delivered your messages because it made a direct network connection

to the recipient’s mailbox in real time, so if VAXmail returned without an

error after you sent the message, you knew it was in the recipient’s mailbox

waiting to be read. Life wasn’t perfect in the golden days of “green screen

email” and today’s clients are definitely a horse of a different color, but

sometimes we don’t seem to have come a lot further than worrying whether

our messages have been delivered.

Life moves on and green-screen email has faded into the past. Over the

last 12 years I’ve connected many different clients to Exchange to read my

email. Exchange 2007 supports a very wide range of clients because it sup-

ports a wide range of client access protocols. Despite frequent predictions

over the years that Internet client protocols would eventually take its place,

MAPI (Microsoft’s Messaging Application Programming Interface

1

)

remains the API that delivers most features and functionality. Microsoft

designed the Exchange RPC protocol to exploit MAPI in a highly efficient

manner, including access mechanisms that closely mimic the MAPI seman-

tics. The investment made in the Exchange RPC protocol and its depen-

dency on MAPI is a major reason why Microsoft has never moved to replace

them with less proprietary protocols. Another reason is that the available

nonproprietary messaging protocols are simply not as functional as the

Exchange RPC/MAPI combination. Many of the features in Outlook

depend on properties exposed through MAPI and depend on the Exchange

RPC protocol, so it is hard to see Microsoft moving away from MAPI in the

medium term.

1. See the Wiki entry on MAPI to learn some of MAPI’s history and background. http://en.wikipedia.org/wiki/

Messaging_Application_Programming_Interface.

582

Apart from MAPI, the other major client families are:

 IMAP4: An Internet client access protocol that is used by most inde-

pendent clients such as Eudora. Also used by Microsoft’s Outlook

Express client.

 POP3: An earlier Internet client access protocol that provides a lower

level of functionality.

 HTTP: The best-known web protocol and used by clients such as

Outlook Web Access.



ActiveSync: Microsoft’s access protocol for mobile clients such as

SmartPhones and PDAs.

When you approach a design project for Exchange, you have to under-

stand what clients are going to be used and why. Each client poses its own

deployment and management challenges and they have their own implemen-

tation and support costs. Clients will change over time and updates will

arrive, but you shouldn’t worry too much about having to update client ver-

sions after the project starts, because in many cases, email client software is

tied to desktop upgrades. Except for small groups, it’s just too expensive to go

and deploy a new version of an email client unless it’s part of a planned regu-

lar desktop refresh. Thus, many companies upgraded to Office 2003 (and

therefore Outlook 2003) as part of their move to Windows XP on the desk-

top and the same thing is likely to happen with Office 2007 and Vista.

Another reason why you shouldn’t worry too much about client versions is

that Microsoft has an excellent record of supporting older clients in new ver-

sions of Exchange. Indeed, you can connect the oldest MAPI client (the

“Capone” client or the “Exchange Viewer”) distributed with Exchange 4.0 to

Exchange 2007. While you won’t be able to take advantage of features that

newer clients can use, such as cached Exchange mode, you will be able to

send and receive email. Almost every browser can connect to Exchange 2007

and run Outlook Web Access, and even the oldest POP3 client can connect

to Exchange 2007.

After your deployment is complete, the next challenge is to deflect all

the user demands to connect the latest and greatest gadgets to Exchange. In

fact, the technical challenge is not difficult because most of the PDAs,

phones, and other email-capable devices that appear use IMAP4, POP3, or

even ActiveSync, if the manufacturer has licensed it from Microsoft. The

challenge is support from the initial connection to the inevitable problems

that occur as users attempt to download email, upload email, synchronize

their contacts and calendars, and use applications such as Windows Live

Messenger. The help desk has probably never seen the devices that users want