Steps to reproduce: 1. Configured CalendarServer-9.0( https://github.com/apple/ccs-calendarserver/releases/tag/CalendarServer-9.0, https://www.calendarserver.org) 2. Added 2 users, postmaster@test.int and abuse@test.int 3. Configured above users account in two separate Thunderbird + Lightning client 4. Created meeting invite in abuse@test.int's account and added postmaster@test.int as attendee Actual results: 1. Meeting is created in abuse@test.int's account 2. Meeting is synchronised in postmaster@test.int's account 3. postmaster@test.int is not able to accept meeting invitation as no accept/decline buttons are shown Expected results: 1. postmaster@test.int is should able to accept meeting invitation Side Note: 1. With same setup, configured iOS clients(iPhone and iPad) and Android clients(CalDavSync) 2. Confirmed expected result -- Sincerely, Prakash P. Autade.