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Proper Exchange licensing

Exchange Server licensing can be a bit tricky. Are your current software licenses up to snuff?

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Microsoft offers a variety of licensing options, which can make sorting out what licensing model is best for you somewhat confusing. In this article, I explain what the license requirements are for keeping your Exchange organization legal.

Licensing requirements for your Exchange servers are pretty straightforward. First and foremost, you need a Windows Server license; Exchange rides on top of the Windows Server operating system, so the underlying OS must be licensed. The Exchange Server license covers you only for the Exchange application, not for the operating system.

In most situations, clients need three different licenses:

  1. A license for the desktop operating system (i.e., Windows XP).
  2. A client access license (CAL) for the Windows server. This license allows the client to legally connect to the server over the network. If you are using per server licensing, then you need a separate CAL for every Windows server on your network. If you are using per seat licensing, then you only need one CAL.
  3. An Exchange CAL. This is the license that permits the clients to access the Exchange server. At one time, Exchange clients also required a license to use Microsoft Outlook, but today an Outlook license is included with each Exchange CAL.

That's about it for basic licensing requirements. As we all know, however, a lot of networks are anything but basic. The licensing model I just described assumes that workstations are running Windows XP and Microsoft Outlook to directly access a server that's running Windows Server 2003 and Microsoft Exchange.

In the real world, people use many other methods to access Exchange. I, for one, use my cell phone to connect with Exchange. Many others use Outlook Web Access (OWA).

If you are using one of these alternative connection methods, it may change your license requirements. For example, if you have employees connecting to Exchange through OWA, you may not need an OS license for the machines that those employees are using. If they're accessing OWA through company laptops running Windows XP, obviously you need XP licenses. However, if they're using personal laptops, a public kiosk, or machines running non-Windows OSes, then you don't have to worry about XP licenses.

You still need the Exchange CAL, though. The rule is that an Exchange CAL is required for any person or device that is accessing Exchange. This includes access through Microsoft Outlook, Outlook Web Access, Outlook Mobile Access, Exchange ActiveSync, or any other messaging interface.

There is one exception, however. Microsoft allows organizations to purchase an External Connector License for Exchange. This license covers anyone who accesses Exchange from the outside world. That way, you don't have to worry about buying an Exchange CAL for every machine that may potentially access your Exchange organization.

Because of the way Microsoft licenses Windows servers for hosting Web sites, you may think you don't need a Windows Server CAL for users who access Exchange solely through the Internet via Outlook Web Access or Outlook Mobile Access (since OWA and OMA are simply Web applications that act as a front end to Exchange). To a certain extent, this is true; Microsoft has never required the purchase of licenses to allow external users to access Web sites hosted on a Windows server.

But, if you read the Microsoft's Windows Server 2003 CAL Overview page carefully, it indicates that Windows Server CALs are unnecessary for users accessing a Web site hosted by the server, only as long as the user is unauthenticated. Unfortunately, OWA and OMA require user authentication, so the normal license requirements do still apply. A CAL would not be required if users were simply browsing a public Web site that was being hosted by your server, though.

As you can see, Exchange licensing can be a little tricky. As such, it is important to occasionally look over your network and make sure that your current software licenses are up to snuff.

About the author: Brien M. Posey, MCSE, is a Microsoft Most Valuable Professional for his work with Windows 2000 Server and IIS. Brien has served as the CIO for a nationwide chain of hospitals and was once in charge of IT security for Fort Knox. As a freelance technical writer he has written for Microsoft, TechTarget, CNET, ZDNet, MSD2D, Relevant Technologies and other technology companies. You can visit Brien's personal Web site at

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