I have DavMail set up to talk to my work Exchange server. This has worked for years with email, contacts, and calendars working fine. I could do normal things like schedule meetings and respond to calendar invites On moving to Thunderbird 78 all hell broke loose in my calendar. First when I opened my calendars I got continuous notifications popping up, 10s of them that would not dismiss. I then find out that my attempts to dismiss notifications triggered responses to be emailed out. My colleagues received literally hundreds of email responses. I have as such had to turn off notifications, and trial read-only mode. When I open Thunderbird the calendar syncs fine. However, when it resyncs it looses about 50% of the events. Each subsequent resync seems to approximately swap which set of events are visible. I have tried toggling offline mode and read only mode to no avail. My intended solution was to downgrade to Thunderbird 68, but Thunderbird 78 has rewritten my profile so I cannot do that. Is there any way to get lightning working on 78? It was perfectly fine. Are there any other options for exchange calendars that allow responses to invites? I see TBsync does not allow invite responses, so is close to useless for me.