Overview
In this article we describe how to find the OAB and EWS URL's which are needed for the Nebula Synchronizer to connect to your calendar system.
How to
Start Outlook and notice the small Outlook icon in the Taskbar / System Tray. Hold the CTRL key and right click on the Outlook icon. 
Select Test E-mail AutoConfiguration.
This will open the test functionality (see screenshot below).
Fill out the E-mail Address and password, and click the Test button.
In Results, you can find the EWS and OAB urls.
- EWS: also shown as the Availability Service URL or OOF URL
- OAB: also shown as the OAB URL
If you get an error message, or no link to the OAB is supplied, it could be due to a setting on the Exchange server. Please contact your (local) Exchange Administrator and they will supply you with the correct URL's.
Glossary
EWS = Exchange Web Services
OAB = Offline Address Book
The format to use for EWS and OAB:
https://outlook.office365.com/ews/exchange.asmx
https://outlook.office365.com/OAB/00000000-0000-0000-0000-000000000000/