I really like the new cards view. But what I miss so much, is that there isn't ANY way to get the size of the message. I receive a good deal of email with (sometimes animated) inline screenshots that are quite large. I want to see this info so that I can decide if I delete the image when replying to make the message smaller.
This info can be anywhere. I don't mind getting it from a context menu. But I saw the new UI plans at https://thunderbird.topicbox.com/groups/ux/Tdb49a4666565e68e-M4aba7d876e0ced9c8d66ca58 and I see a few places where it can be displayed: