I use several sending identities in Thunderbird, e.g. a@mail.example.net, b@mail.example.net, and c@mail.example.net. I have one calendar for each of these sending identities: A, B, and C. That is, the email address selected in Properties for the A calendar is a@mail.example.net, the email address selected in Properties for the B calendar is b@mail.example.net, and the email address selected in Properties for the C calendar is c@mail.example.net.
The a identity is my default sending identity.
I created a new event in Lightning and selected the C calendar. I and clicked "Invite Attendees", and it shows my default email a@mail.example.net filled as a required attendee, but grayed out. I expected this to say c@mail.example.net because I had selected the C calendar, which should be associated with the c@mail.example.net email address. I don't see any option to change the "send from" address.
Is there some way in Lightning way to control which email address is used to send event invitations?