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 recipients mailbox in real time, so if VAXmail returned without an
error after you sent the message, you knew it was in the recipients mailbox
waiting to be read. Life wasnt perfect in the golden days of “green screen
email” and todays clients are definitely a horse of a different color, but
sometimes we dont 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 (Microsofts Messaging Application Programming Interface
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/
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 Microsofts 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 shouldnt 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 its 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 shouldnt 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 wont 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

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