Seeing error 9877 in application log of your Exchange 2010 mailbox server:
Log Name: Application
Source: MSExchangeIS Mailbox Store
Date: 5/2/2013 1:18:21 PM
Event ID: 9877
Task Category: Content Indexing
Level: Error
Keywords: Classic
User: N/A
Computer: <Server Name>
Description:
Content Indexing function 'CISearch::EcGetRowsetAndAccessor' received an unusual and unexpected error code from MSSearch.
along with error 9646:
Log Name: Application
Source: MSExchangeIS
Date: 5/3/2013 7:57:28 AM
Event ID: 9646
Task Category: General
Level: Error
Keywords: Classic
User: N/A
Computer: <Server Name>
Description:
Mapi session "<MAPI session ID> <Object>" exceeded the maximum of 250 objects of type "objtMessage".
These are normal and shouldn't affect anything and can be safely ignored. However, if you want to resolve them you can use MS KB2616127 article for the 9877 and MS KB830829 for the 9646: http://support.microsoft.com/kb/2616127
http://support.microsoft.com/kb/830829
