Error message when you send an instant message to a contact in Communicator 2005: "The following message could not be delivered to all recipients, possibly because one or more persons are offline"

When you send an instant message to a contact in Microsoft Office Communicator 2005, you receive the following error message:

This problem occurs when the user to whom you sent the instant message signs in to Live Communications Server by using TCP. When the user does this, all invitation requests that are received from other Communicator 2005 users are dropped.

How to obtain the hotfix

This issue is fixed in the Communicator 2005 Hotfix Package that is dated June 29, 2007. For more information, click the following article number to view the article in the Microsoft Knowledge Base:

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.