Those user for which EWS Exchange integration is required need to be added to the access group that was previously created on the Exchange server.
Procedure
Open the Active Directory Administrative Center. In the console, select the group previously created for the voicemail server. For our example that was vmpro.
Right-click on the group and select Properties.
Click Add and select the user's email account.
Repeat the process for any other users that need to be added.
