A couple weeks ago Mozilla Thunderbird released version 60 and a lot of extensions became incompatible. Amongst them Exchange Calendar, an extension that allows to sync calendars, tasks and contacts with a Microsoft Exchange Server. That extension has served me well over the last years in my job where we have to use the Exchange Server. Unfortunately it seems that the extension will not be continued anymore, and I had to search for something else.
After trying out some alternatives, I found the extension TbSync. It it uses Exchange Active Sync instead of EWS, so there are currently some limitations with accessing shared calendars and contacts but for everything else it works quite nice. Also the author is actively maintaining it and working on EWS support as well.