Since updating to TB 45.0, when remote images are included within the body of the email, rather than requesting permission for a specific domain(s), each individual image is being treated as a unique 'source'. That is leading to rather long lists being displayed in the pop up which uses up a lot of screen real estate and/or means a long scroll to get to the "allow content from ********" at the bottom of the options. In the case of a large HTML email with multiple images, the list can be huge.