Check the user is connecting to Exchange via MAPI , I had a few setups where users were set to Active Sync instead

In this case, the solution was to run both commands on the exchange server:

Set-AutodiscoverVirtualDirectory “SERVER\Autodiscover (Default Web Site)” -WSSecurityAuthentication $True

Set-WebServicesVirtualDirectory -identity “EWS (default web site)” -WSSecurityAuthentication $true

This two command solved my problem

Tags: Calendar, could not be updated, exchange, Outlook

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