To install, download and save this file. Then from Thunderbird, open Tools/Add-ons, click on the Addon tools button and select “Install Add-on From File”. Install the downloaded file, then restart Thunderbird.
Alternatively, just go to the addons manager in Thunderbird, search for ExQuilla, and install it from there.
If you are having trouble, make sure that you know the correct internet address to open a web page to see your email, for example “https://yourcompany.com/owa” Replace the “owa” with “EWS/Exchange.asmx” and enter that as the Exchange URL. So for this example, the Microsoft Exchange URL would be: