I thought that I would fire off a quick blog post about this issue as it happened to me recently: a number of users reported that they could not reply to email messages, or compose new messages, when accessing Outlook Web Access (OWA) from PCs running Windows Vista. They were able to log in and read messages, but when trying to send a message, the text-entry box was unavailable.

The issue was definitely related specifically to the conbination of Vista and IE7, rather than IE7-specific, as IE7 on a Windows XP machine was not affected, and running Firefox on Windows Vista was also not affected.

A bit of Google action revealed that the issue is down to the fact that support for DHTML (Dynamic HTML - HyperText Markup Language) has been retired on Windows Vista, and a patch must be applied to the Exchange 2003 Server to effectively re-write the HTML code behind the OWA web site.

The patch can be downloaded from the Microsoft web site here:

http://www.microsoft.com/downloads/details.aspx?FamilyID=5bc06e8a-08eb-4976-bc68-a03ebe3a2552&DisplayLang=en

The pre-requisites listed for the patch include Exchange 2003 Service Pack 2. Our Exchange Server has service pack 2 installed - as testified to by the fact that we have been enjoying push email service for a number of years now.

Problem solved you would think. Apparently not.

When I went to install the patch I received an error message indicating that the patch could not be installed because service pack 2 was not installed on the server.

A bit more digging, and a lot of swearing at my screen, I came across an article indicating that there are 2 principal versions of service pack 2 for Exchange currently in circulation - one of them is known as the 'technology preview release' and was made available to TechNet subscribers prior to being released generally through Microsoft Update. The patch did not like the fact that I had the preview release, even though the funcitonality is exactly the same.

To find out if you are running the preview release, or the full release, open Registry Editor and browse to:

HKEY_Local_Machine\Software\Microsoft\Exchange\ServicePackBuild\

If the value reads 1DC7 then you have the preview, if it reads 1DD6 then you have the full release.

The solution was to download and reinstall Exchange Server Pack 2 over the top of the existing installation. Once installed the patch then installed also...and Vista users can now use OWA properly.