Error while opening address book. Error Code: 0x00040380 (MAPI_W_ERRORS_RETURNED)

Error while opening address book. Error Code: 0x00040380 (MAPI_W_ERRORS_RETURNED)

If you get the following error in the Application Event log:

The AgendaX Update Service reported the following error:
General Error - Output: Error while opening address book.
Error Code: 0x00040380 (MAPI_W_ERRORS_RETURNED)
Description: The connection to Microsoft Exchange is unavailable. Outlook must be online or connected to complete this action.
MAPI was unable to load the information service EMSMDB.DLL. Be sure the service is correctly installed and configured..

and you are connecting to Office 365, please follow the steps below to solve this problem:

Add the following keys to the registry, logged-in with the user that is used to run the AgendaX Update Service:


EnableADAL (DWORD) 1
DisableADALatopWAMOverride (DWORD) 1

16.0 is for Outlook 2016, 2019 and Outlook 365. If you use Outlook 2013, you have to update to Outlook 2016 or above as Microsoft does not support connections to O365 with earlier clients anymore.

Go to Control Panel / Credentials Manager / Windows Credentials and delete all credentials starting with MicrosoftOffice16_Data.

Reboot the server (not always necessary), recreate the Outlook profile that you have configured AgendaX to use, turn off Exchange Cache Mode in the profile, start Outlook with this profile, close Outlook again.

If you are prompted for username / password, please activate the checkbox 'Save password'.

After these steps, the error logged to the Application eventlog should go away.

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