Exchange MAPI Session

Event ID: 9646
Source: MSExchangeIS
Description:
Mapi session "/o=Marvell/ou=MAPL Exchange/cn=Recipients/cn=gjiao" exceeded the maximum of 32 objects of type "session".
For more information, click http://www.microsoft.com/contentredirect.asp.

Solution:
Edit Registry
MyComputer\HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeIS\ParametersSystem
Add new key "Maximum Allowed Sessions Per User"
Type: DWORD
Value: 64