The Exchange Web Services Connectivity Test dialog is opened by clicking the Test Connectivity... button in the relevant group on the Environment Configuration dialog:
This dialog is used to test connectivity to your organization's Exchange Web Services platform. This is helpful to test that the deployment of signatures will work as expected using the account specified on the Environment Configuration dialog.
By default, the current Windows user is selected for the test. To choose a different user against which to test, click the ellipses button ("...") next to the user.
When ready, click the Test button. If the tests complete successfully, you will be presented with a confirmation message, giving the choice to open the detailed results dialog. It the tests fail, the results dialog will open automatically.
Once testing has been completed, click the Close button to close the dialog.