Event ID 9646: Mapi session exceeded the maximum objects type

Hi

On Exchange Servers you get the Event:

Event ID 9646 : Mapi session /o=My Company/ou=First Administrative Group/cn=Recipients/cn=user” with Client Type WebServices exceeded the maximum of 250 objects of type “objtMessage”.

How to solve :

First, Do A Backup To Registry (on all server that you change).

1. On the server, start up regedit.
2. Navigate to the registry key:HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeIS\ParametersSystem
3. If not present, create a new key called MaxObjsPerMapiSession.
4. Inside MaxObjsPerMapiSession, create new DWORD (32-bit) values for each of the MAPI object types you wish to increase:
   • Name = the name of the MAPI object type (e.g. objtMessage).
   • Value = the maximum number of connections allowed for this type, per user.
   • Type = DWORD (32-bit)

Attached Table with the most common :  “Types” (MAPI object type)

After you Create the Registry You must restart : Microsoft Exchange Information Store Service on all your Mailbox Server

Shmuel H.