Event Calendar Plus can use WebDAV or Web Services protocol to establish connection with Exchange servers. The WebDAV protocol exists in all Exchange versions, but the Web Services require Exchange 2007 or up. It is recommended to use the newer Web Services protocol whenever available.

To define a connection to the Exchange calendar first you need to decide on the authentication method. Event Calendar Plus supports the following authentication methods:

1. Impersonated Identity – NTLM Authentication using an impersonated user identity. Please note that the impersonated user must have a mailbox or have at least read access to the mailbox of the user, whose name appears in the Username textbox. This authentication method supports both NTLM and Kerberos but does not support Basic authentication. This configuration will present a static calendar either belonging to the impersonated account or to the user whose mailbox is entered in the Mail Address textbox. Enter the domain\username in the Username textbox and the password in the Password textbox.
2. Kerberos – the current user’s identity is passed by the SharePoint server to the Exchange server. The authentication method of SharePoint must be set to Kerberos and the SharePoint server must be configured as Trusted for Delegation in the Active Directory.
   This configuration will present a dynamic calendar belonging to the current user viewing the web part page.
3. Basic – username and password combination is passed in clear text to the Exchange server. The Exchange server web application must be configured to allow basic authentication. If the Mail Address is left blank, the mailbox of the authenticated user is shown, otherwise passed credential must have at least read access to the entered mailbox.
   This configuration will present a static calendar either belonging to the entered credentials or the user whose mailbox is entered in the Mail Address textbox.

NOTE: the entered username and passwords are stored encrypted in the web part properties, so there is not risk of credentials theft.