Like previous releases, the current version (6.16.0.7) of Skype for Business for Android mobile devices exposes 2 Exchange configuration options namely “Skype for Business Anmeldeinformationen verwenden” and “Server automatisch erkennen”.
If you disable the latter option, specify manually the “Exchange-Webdienste FQDN oder URL” and press OK to save the changes, the settings should take effect in an instance or so. The appearance of a list of upcoming skype4b meetings on the main and Calendar tab confirms that Exchange Web Services (EWS) connectivity is functioning as expected.
Nevertheless when you revisit the same Exchange configuration settings, you find that the “Skype for Business Anmeldeinformationen verwenden” is deactivated unexpectedly. Additionally, “Server automatisch erkennen” is now mysteriously re-enabled. By turning it off again, you see that the previously entered EWS FQDN/URL is still intact.
This is apparently a User-Interface only issue; from a functional perspective, everything should continue to work as normal until Microsoft fixes this UI quirk. Otherwise, you may have to logoff and sign-in to have the EWS settings take effect (or toggle the switches explicitly).