You cannot use the search function to search for mailbox items in a Microsoft Exchange Server 2010 environment. This issue typically occurs if the mailbox in the environment contains documents that have large file sizes.
This issue is caused by a deadlock issue in the Msftesql.exe process. Exchange Server 2010 uses the Msftesql.exe process as an indexing service.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.