I couldn't find a way to configure out of office auto reply mechanism in Thunderbird like there is in Outlook. The only way i have found through searching online is to create a message filter but that needs the laptop and Thunderbird to be running all the time, which is stupid in my view. Please share if you know a way.
Thunderbird and Outlook are local E-Mail-Clients so they must be running to answer your E-Mails. The difference is, that Outlook is often connected to an Exchange-Server which sends those Messages on your behalf (and runs all the time btw.). Thunderbird doesn't have such a Server equivalent and therefore doesn't provide the functionality you are asking for. You need to find out which Mailserver your company is running and configure your out-of-office note there (ask an Admin).
Probably we can work with the add-on for Lightning being worked upon which definitely solves the extended out-of-office functionality but lacks in caching of events. How you do it is.. 1. Install the add-on from https://www.1st-setup.nl/wordpress/?page_id=133
Map it using the EWS setting as mentioned in the FAQ.
Whether use the calendaring or not it do a RIGHT_CLICK on the Calendar -> Click Out_Of_Office_settings
That is all you need.