tested with: thunderbird 68.6.0 (64-bit) on GNU Linux Debian 10 if one uses the build in calendar of thunderbird (it was called sunbird, was replaced by lightning) go into advanced config editor: (about:config) type: calendar.alarms.showmissed and double-click on the entry … Continue reading thunderbird calender reminders keep popping up – do not show reminder of passed old “missed” events