KB Article: http://support.microsoft.com/kb/2616127
Consider the following
scenario. By default, Exchange Search is enabled for a mailbox database in a Microsoft Exchange Server 2010 environment. You use Microsoft Outlook in online mode to search a mailbox for a keyword or phrase that contains a single letter or a single digit. In this scenario, you receive the following error message even though there are matches for the keyword in the mailbox:
No matches found for "keyword".
Additionally, the following event is logged in the Application log:
Log Name: Application
Source: MSExchangeIS Mailbox Store
Event ID: 9877
Task Category: Content Indexing
Content Indexing function 'CISearch::EcGetRowsetAndAccessor' received an unusual and unexpected error code from MSSearch.
Mailbox Database: Mailbox Database
Error Code: 0x80041606
0x80041606 = QUERY_E_TOOCOMPLEX