I followed the instructions from
https://edx.readthedocs.io/projects/open-edx-release-notes/en/latest/bulk_email.html
It wasn’t clear to me what the “Require course email auth” option does based on that documentation. So I selected it. Subsequently I didn’t see any option for emailing students from the Instructor live view. So since I couldn’t then just click into the configuration and disable it, I had to hit “add bulk email flag” again and disable it this time. And then the option actually showed up.
So the question is, what does “Require course email auth” actually do, and how is it meant to be used?
(Note to future people: I recently learned that studio.my.lms.com/admin django doesn’t show you the same stuff as my.lms.com/admin, so you need to go to the my.lms.com/admin version for the “BULK_EMAIL” option to even be visible))