About d.3one
Useful things to know about storing and displaying e-mails in d.3one
If you or your users want to use the Offline Store in Microsoft Outlook, you must ensure that basic authentication is enabled for Microsoft Exchange Server. The Windows user account that is currently logged in is used for authentication. Due to this restriction, the Windows user account must also have the mailbox.
To use the Offline Store, you can only use the EWS interface in combination with basic authentication.
If you are using Microsoft Office 365, you must synchronize the on-premises Active Directory with the Azure Active Directory so that the users are identified by both directory services.