Hi All,

can some one please help to resolve this issue.

Probe: EdiscoveryDeepTestProbe/ONLINE-MXDB-001
Latency: 0ms
Error: MapiExceptionMdbOffline: Multi Mailbox Keyword Stats Search failed. (hr=0x80004005, ec=1142)
Diagnostic context:
    Lid: 49384  
    Lid: 51176   StoreEc: 0x476     
    Lid: 40680   StoreEc: 0x476     
    Lid: 46696   StoreEc: 0x476     
    Lid: 63080  
    Lid: 38504   StoreEc: 0x476     
    Lid: 58984  
    Lid: 34408   StoreEc: 0x476     
Details:
Log:

-------------------------------------------------------------------------------

States of all monitors within the health set:
Note: Data may be stale. To get current data, run: Get-ServerHealth -Identity 'PRD-MXSRV001' -HealthSet 'Ediscovery.Protocol'

State               Name                                    TargetResource                     HealthSet                     AlertValue     ServerComponent     
-----               ----                                    --------------                     ---------                     ----------     ---------------     
NotApplicable       EdiscoveryDeepTestMonitor                                                  Ediscovery.Protocol           Healthy        None                


States of all health sets:
Note: Data may be stale. To get current data, run: Get-HealthReport -Identity 'PRD-MXSRV001'

State               HealthSet                     AlertValue     LastTransitionTime       MonitorCount        
-----               ---------                     ----------     ------------------       ------------        
NotApplicable       ActiveSync                    Healthy        28/04/2015 21:32:59      2                   
Online              Autodiscover.Proxy            Healthy        25/11/2014 14:42:32      1                   
Online              ActiveSync.Proxy              Healthy        25/11/2014 14:42:32      1                   
Online              RWS.Proxy                     Healthy        25/11/2014 14:45:37      11                  
Online              ECP.Proxy                     Healthy        25/11/2014 14:42:32      1                   
NotApplicable       ActiveSync.Protocol           Healthy        25/11/2014 14:47:56      7                   
NotApplicable       Autodiscover.Protocol         Healthy        25/11/2014 14:46:45      8                   
Online              EWS.Proxy                     Healthy        25/11/2014 14:42:32      1                   
Online              OWA.Proxy                     Healthy        25/11/2014 14:42:32      2                   
Online              RPS.Proxy                     Healthy        25/11/2014 14:45:41      6                   
Online              OAB.Proxy                     Healthy        25/11/2014 14:42:32      1                   
NotApplicable       EDS                           Healthy        25/11/2014 14:55:46      43                  
NotApplicable       ECP                           Healthy        25/11/2014 15:39:21      12                  
NotApplicable       EventAssistants               Healthy        25/11/2014 15:06:30      20                  
NotApplicable       EWS.Protocol                  Healthy        25/11/2014 14:47:27      8                   
NotApplicable       AD                            Healthy        25/11/2014 14:50:23      24                  
Online              FrontendTransport             Healthy        28/04/2015 22:05:26      12                  
NotApplicable       Monitoring                    Healthy        25/11/2014 14:47:19      20                  
NotApplicable       DataProtection                Healthy        1/04/2015 9:55:52        106                 
Online              HubTransport                  Healthy        14/04/2015 7:36:00       96                  
NotApplicable       MailboxTransport              Healthy        25/11/2014 14:50:46      31                  
NotApplicable       MSExchangeCertificateDeplo... Disabled       1/01/0001 1:00:00        2                   
NotApplicable       OWA.Protocol.Dep      

Hi,

Do you have deploy DAG or run mailbox server during this error arise?

Because server queue size has been limited, you might get this error when implementing multi-Mailbox search with lots search options.
Here's an blog about it, please refer to: http://blogs.technet.com/b/exchangesearch/archive/2011/08/16/discovery-searches-may-fail-in-exchange-2010-due-to-a-large-number-of-terms-in-query.aspx

If the issue persists, you can reseed the search catalog to solve this issue. For your reference: https://technet.microsoft.com/en-us/library/ee633475(v=exchg.150).aspx

Thanks