Installing your first Exchange 2010 CAS or the truth about Exchange2003Url – Part 1

The Exchange2003Url is a new parameter in the Set-OwaVirtualDirectory cmdlet on Exchange 2010. Although Microsoft documentation clearly states that "The Exchange2003Url parameter specifies the Outlook Web App URL for Exchange 2003 mailboxes." It is all over the net that this parameter is also used to redirect requests to Exchange 2007 mailboxes!

I have no idea where this idea is coming from but I can assure you that is not the case.

Upgrading from Exchange 2003 to Exchange 2010

If you are upgrading from exchange 2003 you should know that an Exchange 2010 CAS cannot communicate directly with an Exchange 2003 mailbox. Thus you will need to publish at least 2 URLs one for your Exchange 2010 CAS and one for you Exchange 2003 Back End server or Front End server.

We will assume that https://owa.yourdomain.com/owa will point you to your exchange 2010 CAS server and https://ex2k3.yourdomain.com/exchange will give you access to your exchange 2003 back end or front end server.

By running, on your Exchange 2010 server,

Get-OwaVirtualDirectory -server Exchange2k10 | Set-OwaVirtualDirectory -ExternalName https://owa.yourdomain.com/owa -Exchange2003Url https://ex2k3.yourdomain.com/exchange

you are instructing your exchange server to redirect all request from users with mailboxes on Exchange 2003 to https://ex2k3.yourdomain.com/exchange

By default this is a silent redirection and it will work seamlessly to the client if you have Form Based Authentication enabled on your Exchange 2003 back end/front end server.

Unfortunately if form based authentication is not enabled the user will be prompt again for credential and after it will fail with 500 Internal error at https://ex2k3.domain.com/exchweb/bin/owaauth.dll.

However many of us who are using ISA/TMG for publishing don't want to enable form based authentication at the server level.

As a workaround for this issue you can disable the silent redirection by issuing to following  on your Exchange 2010

Get-OwaVirtualDirectory -server Exchange2k10 | set-OwaVirtualDirectory -LegacyRedirectType manual

This will now offer the user a page with the corresponding legacy URL, although users will have to authenticate again, they will face no error after doing so.

Part 1: Installing your first Exchange 2010 CAS in an Exchange 2003 organization
Part 2: Installing your first Exchange 2010 CAS in an Exchange 2007 organization
Part 3: Installing your first Exchange 2010 CAS in a mixed Exchange 2003/2010 organization

About Antoine Khater

I have been working in IT consultancy and solution integration since 1998 and I consider myself lucky to be, one in a few, making a living out of my passion. I am also member of the famous Experts Exchange (profile here) online community where I try my best to share what I have learned along the road.