Exchange 2016:- Event ID 9646: Mapi session (redacted) with client type MoMT exceeded the maximum of 32 objects of type Session
In your Exchange 2016 environment, you might have noticed the following Event (Event ID 9646) being logged:
- Mapi session (redacted) with client type MoMT exceeded the maximum of 32 objects of type Session
To resolve this issue, you can create a registry key on the server and then restart the Exchange Information Store.
- HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeIS\ParametersSystem\Maximum Allowed Sessions Per User
The value for “Maximum Allowed Sessions Per User” Value data set to 500 and ensure it is set to a Decimal Value:
Once done, you can go to Services and restart the Exchange Information Store or reboot the server for the changes to take effect.
Hope it helps.