You use Microsoft Office Outlook in online mode in a Microsoft Exchange Server 2010 environment.
You set the Mark items as read when viewed in the Reading Pane option in Outlook.
Note To set this option, follow these steps:
In Outlook, click File, select Options, and then select Mail.
In the Outlook panes field, click Reading Pane.
In the Reading Pane window, click to select the Mark items as read when viewed in the Reading Pane check box.
You search for a keyword, and some message items are returned.
In this scenario, the returned message items can disappear from the search results view after a while. This occurs when messages are marked as unread in the view.
The issue occurs because Exchange Server 2010 removes the returned message items of which the read/unread attribute has changed from the search result view when it updates the view. However, it does not add the message items back to the search result view after the update is complete.
To resolve this issue, install the following update rollup:
2661854 Description of Update Rollup 2 for Exchange Server 2010 Service Pack 2
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.