For more information, see Digital certificates and encryption in Exchange 2016 and Set-AuthConfig. New installations of Exchange Server include a default authentication certificate. The server must have a valid authentication certificate in order for the server to issue valid identity tokens.Many add-ins require EWS to function properly. Exchange Web Services (EWS) must be enabled and must be exposed to the Internet.The server must be Exchange 2013 or later.However, for users connected to on-premises installations of Exchange Server, the following requirements apply. If the user is connected to Microsoft 365 or, mail server requirements are all taken care of already. If the client is configured to connect with POP3 or IMAP, add-ins will not load. When configuring the client, the user must choose an Exchange, Office, or account type. The client must be connected to an Exchange server or Microsoft 365 using a direct connection.
The client must be one of the supported applications for Outlook add-ins. For Outlook add-ins to load and function properly, there are a number of requirements for both the servers and the clients.
