Ever wondered how Exchange Server evolved over the years? And how come Exchange Server 2007 shows "8.0" as its version number? Here is a brief history of time... it might add a bit to the known history!
First Exchange proof of concept was in the early 90's. Development team usage only.
Mercury - we couldn't get Exchange to scale past 25 users. We were bleeding internally with Xenix mail, so we figured that we'd keep Exchange alive but just use it as a MIR (Microsoft Internal Release). A perf and scale team was put in-place to see what we could do about the abysmal performance.
Touchdown - the perf and scale team figured out the important issues, and Exchange once again had the potential to become an external release, marketed and sold by Microsoft. Indeed, after several test releases, we shipped in early '96 as Exchange 4.0
4.1 - Exchange 4.0 spent a long time in development, but it was a little rough around the edges. We immediately started work on a 4.1. After having implemented X400 as the primary messaging protocol and an X500-like directory structure, we quickly realized that this Internet 'thing' was really going to take off. It started to become obvious that we needed more than a .1 release. The 4.1 moniker was dropped and we were now working toward 4.5. After implementing several ground-breaking protocols such as SMTP and LDAP v2, this was certainly not a dot release. We shipped as Exchange 5.0 in early '97.
Exchange 5.0 brought another important technical addition - the introduction of a Web-based e-mail client called Exchange Web Access (EWA). EWA was subsequently renamed Outlook Web Access (OWA). EWA was revolutionary for its time. It allowed employees or other individuals with mail stored in an Exchange 5.0 or later server to use a web browser to access their e-mail from anywhere at any time. In other words, the Exchange server provided the necessary information and interface through the web browser, no special e-mail client application was required on the user's machine.
While on the subject of Exchange 5.0:
If you still have an Exchange 5.0 CD around, there is an Easter egg on the CD in the form of a file called EXGL32.DLL. Rename that file to .AVI and view it... it is essentially credits for all the people that worked on Exchange 5.0 and while at it, we made some fun about the versioning in it too. Just so you get an idea:
The Exchange 4.1 Team! Oh... wait[...]