Exchange Web Services URL (Uniform Resource Locator) can be obtained from the the Client Access Server EWS (Exchange Web Services) configuration. The URL section allows you to modify or define (a new) Subscription Callback URL. Microsoft Office 365 uses the Subscription Callback URL to send information to your own Exchange Server when it is requested.
You can change the Exchange Web Services URL, though it will automatically be filled with the URL defined during the installation.
For Exchange Server Online, the Exchange Web Services URL does not need to be defined, since the location of the data will change continuously.
You can define the Subscription Callback URL, e.g.: http://SERVERHUB:9008/ExchangeConnector.web
You can define the Heartbeat Interval in minutes.
The connection with the Exchange Server will be checked using this interval.