Exchange Server Operating Modes

by  Sam C. Chan

First published: December 1, 2005
Last Revised: May 21, 2006

In the 10 years I have been using Exchange Server (since 1996, the NT4 era), I have noticed an interesting phenomenon:  You'll often hear: "If you have an Exchange Server... then you need to have such and such..." or  "... then here's how you'd do such and such..."

In the fantasy world, you're either a multi-national Fortune 100 company with a massive fleet of Exchange servers and elaborate hierarchy, or you're Joe consumer with a stand-alone computer (no LAN, no router, no server) using your ISP for email. In the real world, there are many shades of grey.

When it comes to Exchange Servers, IT practitioners fall into 2 categories: a tiny elite group of gurus with their heads buried in technical complexity; and the rest―the overwhelming majority, who know absolutely nothing about even the basic email process beyond the plug-and-play-and-click-send. Both groups are ignorant of the fact that there are multiple operating modes, each with its pros and cons. The correct one must be chosen, to achieve sensible, optimal (and in some cases, viable) results.

In 2003, with the advent of Exchange 2003/Outlook 2003, and its new and much-welcomed  Cached Exchange Mode, I have refined my IT doctrines to formally define what I term Exchange Server Operating Modes. There are many specific and tangible roles, purposes and rationale behind them. The realization and comprehension of such concept is the first step toward eliminating frustrations, and solving all those supposed "mysteries."

All the dos and don'ts, procedures, infrastructural requirements, skill set prerequisites, and best practices are driven by the mode. Here, I have provided a very brief sketch diagram, along with some basic notes, to give you a glimpse into what it is all about.

If you're a seasoned and advanced professional, who had always been puzzled by, and subsequently, been pondering such issues... this would no doubt instantly be one of your memorable eureka! moments. This conceptual framework along with its checklist would allow you to see the problem in a new light, and immediately put your own know-how to productive use.

If you're a business manager, or a junior IT practitioner, this will serve as a road map and allow you to quickly ask all the right questions, and learn the pertinent items without wasting time in irrelevant areas, or worse... following popular myth and conventional wisdom, and going down the wrong path to disaster!

Happy messaging and collaborating!

Exchange Sever Operating Modes - by Sam C. Chan - Bravo Technology Center

Level 0 1 2 3
EXG Cached Mode Stand-alone EXG Cached EXG Cached EXG Cached
Domain MX points to Hosting ISP POP Hosting ISP POP Hosting ISP POP Exchange Server
Static IP Address No No No Yes
Depends on DNS/MX Yes Yes Yes Yes
Depends on POP Yes Yes Yes No
Depends on EXG No No Yes Yes
Uses HQ Bandwidth No No Yes Yes
ISP Webmail Yes Yes Yes No
Live Full set of email No Req. Master Client Yes Yes
Redundant Data No Yes Yes Yes
Direct Control of Acct Yes Yes No No
Rich Features via HTTP No Yes Yes Yes
Desk Roaming on LAN No Yes Yes Yes
Public Folders No Yes Yes Yes
Global Contacts No Yes Yes Yes
Shared Calendars No Yes Yes Yes
Free/Busy status No Yes Yes Yes

Issues to Consider:
  • old messages
  • new messages
  • control of email acct
  • quota
  • HQ bandwidth: downlink/uplink
  • webmail support
  • OWA support
  • admin complexity
  • users complexity
  • Exchange server dependency
  • POP Sever dependency
  • static IP


Major deficiencies/risks
Significant Requirements/Limitations
Acceptable Requirements/Limitations
Significant Advantages

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