You send a meeting request to an external user from a Microsoft Exchange Server 2007 environment.
The external user accepts or declines the meeting request.
Certain letters in the external user’s email address have different capitalization in the following locations:
The MAILTO address of the meeting request that you send to the external user.
The FROM header of the meeting response that you receive from the external user.
For example, you send a meeting request to an external user by using an address Testuser@testdomain.com. However, the external user’s address in the FROM header of the meeting response that you receive is email@example.com.
You open the meeting request to track the status.
In this scenario, the meeting response status indicates the meeting request is tentatively accepted. Therefore, you cannot track the meeting response status from the external user correctly.
Note If you open the meeting response from the external user, the message subject field show the correct status (accept or decline)
This issue occurs because Exchange Server 2007 performs a case-sensitive search incorrectly when it tries to determine the attendee who responds to the meeting request. The search fails in the scenario that is described in the “Symptom” section.
To resolve this issue, install the following update rollup:
2530488 Description of Update Rollup 3 for Exchange Server 2007 Service Pack 3
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.