Exchange 2003 only wins with WINS.

Since Microsoft released the Release Candidate for Exchange 2010, I figured that a look back at some things in Exchange 2003 are well in order.  After all, a lot of folks are currently on that platform, and waiting for 2010 to RTM before they upgrade.

So today, let’s take a look one of the components of Windows that Exchange 2003 needs to have in place, but that causes confusion and doubt every time it comes up in conversation.

The Windows Internet Naming Service (WINS) is a component of Windows Server NT4, 2000 and 2003 that – as its name implies – translates NetBIOS names into internet names and addresses.  And to be absolutely clear on the subject, Microsoft *requires* the installation of WINS for full functionality of Exchange 2003.  Here’s the proof.

The reasons for this insistence on having WINS present in Exchange 2003 are varied, but the controversy over the requirement has raged ever since Exchange 2003 was released.  The confusion stems from the apparent dichotomy between the fact that 2003 is supposed to be totally DNS integrated, and the view that NetBIOS dependencies make it look as though it is not.  Another reason for confusion is that even though Microsoft says that the installer will not run properly without WINS in place, many clients have managed to install Exchange 2003 without the WINS services running at all, or worse yet; with the WINS system improperly configured and malfunctioning.

Exchange 2003 leverages Active Directory (AD) DNS for nearly all name resolution functions, from finding other servers in the local environment to finding SMTP hosts for external mail destinations.  For internal resolution, Exchange can leverage AD and Global Catalog servers to find things, as long as everything in the domain in question is using Windows 2003 or higher, and configured appropriately.  MAPI systems in 2003 also can use DNS to find Exchange servers (Outlook 2003 and up) or to locate other resources.  So if you are in a pure Windows/Exchange/Outlook 2003 or higher environment, and you have only one Active Directory site, then you’re all set without WINS.

That last sentence is key to figuring out where the requirements for WINS come from, and where most of the confusion stems from as well.  Most environments that use Exchange 2003 still have mixed-mode domains, possibly even some Windows 2000 servers around.  They’ve also brought legacy systems up to Windows 2003 over the years, meaning that older names and objects may still be preserved in AD.  So if an Exchange 2003 server needs to find a resource that AD only has a “short name” (non-fully qualified domain name) for, the traditional method to find that resource would be WINS, not DNS.

This also comes into play if you have multiple AD sites across multiple physical locations.  Since short names don’t translate properly from site to site, or domain to domain in the same Forest, WINS is necessary to translate the resources name into a location for the resource itself. 

Finally, any legacy Outlook clients (XP and earlier) rely on WINS to find all resources, as the MAPI clients they contain don’t understand DNS lookups at all.  So if you have any older Outlook clients running around, you’ll need to ensure WINS is configured properly.  Similarly, ExMerge relies on WINS since it was a hold-over application from earlier Exchange versions, and therefore never designed to leverage DNS.

So, until your environment moves up to Exchange 2007 or 2010, and a Native 2003 or Native 2008 Domain architecture, you’re stuck with WINS.  The good news is that WINS is just another component of Windows in 2003, and therefore not a bear to implement at all.  Go to Add/Remove Programs and choose to install Windows Components.  You’ll need your OS CD’s to finish the install, and as always; be sure to Service Pack after you are done and run Windows Update.  There have been many changes and patches to WINS over the years, especially in light of recent attacks against it.

WINS is a legacy system that is – thankfully – going away as we move toward Exchange 2007 and 2010 native environments, and as legacy Outlook clients are phased out.  Until then, make sure you keep up with WINS patches and ensure it is installed and configured. Not doing so can cause resolution problems for Exchange 2003, and installing it is a requirement from Microsoft, so take the time now to make sure your WINS systems are operating full steam.