Wednesday, March 30, 2005

A Brief History of Exchange Server


A brief history lesson, for those of us that have lived through this, it is great to see where we have been.

Microsoft Exchange Server started its life as Exchange Server 4.0, shortly after Microsoft discovered the Internet.  Prior to Exchange, Microsoft had another email product called Microsoft Mail. The last version of MS-Mail was 3.5 and it was released in September of 1995. Microsoft hoped that by numbering the first version of Exchange as 4.0, it would convince users to migrate quickly.

Regardless of the version number, Exchange 4.0 was a version 1.0 product and it was not an upgrade to MS-Mail 3.5. To get from MS-Mail 3.5 to Exchange Server 4.0 was a full-scale migration. Exchange 4.0 also had a number of severe limitations and somewhat limited functionality (especially when compared to the products available today). However, it introduced many capabilities that are absolutely recognizable even in today’s much more mature product. Exchange Server 4.0 was followed by Exchange Server 5.0 and then by Exchange Server 5.5.

Exchange Server 5.5 was the first version of the Exchange product line to really take off. Exchange Server 5.5, especially by service pack 3, was a very usable product. It is estimated that, at this writing (very early 2005) that over 25% of Exchange customers are still using Exchange Server 5.5; even despite the fact that two major versions of Exchange have been released since the release of Exchange Server 5.5. It was, and still is, a very stable product.

Exchange Server 5.5 was the first version of Exchange to truly support “the Internet” with an Internet Mail Connector (IMC). Therefore, if companies are still using older versions of Exchange Server, then they are probably not connected to the Internet, at least for email! I doubt that very many copies of Exchange Server prior to version 5.5 are still in operation.

The releases of Exchange Server up to and including Exchange Server 5.5 all shared a common feature – a directory which was maintained by the Exchange Server itself. For the purposes of this discussion, a directory is a list of items (such as subscribers, distribution lists, contacts, public folders, routing tables, etc.) and all of the attributes (information and data) about each of those items. All of the items and their attributes were stored in a database maintained by Exchange – and this database was not part of the operating system.

In a revolutionary change, Exchange 2000 Server moved the directory into the brand new Active Directory. Starting with Exchange 2000 Server, Exchange requires Active Directory and heavily uses some of the features and functionality of Active Directory.

Since the Active Directory database was originally based on the Exchange database technology, it was a natural step.

There were other revolutionary changes in Exchange 2000 Server – among them the inclusion of a Conferencing Server (which provided additional collaboration capabilities to Exchange) as well as Instant Messaging capabilities. These changes were moved back out of Exchange Server and into a separate product (Microsoft Live Communications Server) as of Exchange Server 2003.

As a minor aside, the change in name between all prior versions of Exchange Server Version and Exchange 2000 Server was another modification that lasted for only a single product release.

The movement to Active Directory with Exchange 2000 Server also significantly changed the administrative model for Exchange. Historically, an Exchange administrator could control everything about an Exchange site – the subscribers, the mailboxes, the distribution lists, server configuration, etc. With the integration to Active Directory, however, that is no longer always the case. Exchange management is now separate from user and group management (groups include distribution groups, which were known as distribution lists in Exchange 5.5 and before).

In larger companies, this administrative split makes very good sense, as messaging and collaboration are just applications. Being an administrator of the messaging system shouldn’t provide application level administrators the full administrative control of the computer network too. For many (if not most) smaller companies, the distinction is meaningless and it often doesn’t seem to make any sense – why it is now necessary to use two programs for administration, whereas in Exchange 5.5 and earlier, everything could be done in a single program.

Thankfully, for these smaller environments the multiple administrative consoles may be merged into a single custom console providing the single point of administration that these companies are used to.

Exchange 2000 Server represented a major change to the core architecture of the Exchange product, and in some ways the integration with Active Directory again made it a version 1.0 product. Even so, Exchange 2000 was a significant improvement over Exchange 5.5. Many of the Exchange 2000 deficiencies were corrected in Exchange 2003. Exchange 2003 has proven itself to be an extremely stable and feature rich platform.

Table 1-1. Versions of Exchange Server and related products

Product Name

Release Date

Microsoft Mail 3.5

September 12, 1995

Exchange Server 4.0

June 11, 1996

Exchange Server 5.0

May 23, 1997

Exchange Server 5.5

February 3, 1998

Exchange 2000 Server

November 29, 2000

Exchange Server 2003

September 28, 2003


The release of Exchange Server 2003 also integrated a significant new feature set into Exchange – Mobility. Mobility provides access to Exchange features and functionality from non-traditional clients – such as Windows Mobile Clients (Pocket PC 2002 and Pocket PC 2003 with Microsoft ActiveSync) as well as any PDA client which supports cHTML (via Outlook Mobile Access or OMA).

Prior to Exchange Server 2003, the available mobility functionality was present in another server product – Microsoft Mobile Information Server (MMIS). Its functionality was somewhat less than what is present in the current version of Exchange. The releases of MMIS were as shown below.

Table 1-2. Versions of Microsoft Mobile Information Server

Product Name

Release Date

Mobile Information Server 2001

September 16, 2001

Mobile Information Server 2002

May 21, 2002


As of this writing (very early 2005), Exchange Server 2003 has had one service pack released, with a second service pack expected in the second quarter of this year. There have also been several “add on” feature packs released to add functionality to Exchange Server 2003 (IMF – Internet Message Filter being the chief one among them).

The next version of Exchange Server, codenamed E12, is expected in the second half of 2006.

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