Undelivered messages don't have a context menu
As stated in the title, undelivered messages (with the small no entry sign on the right) don't have a context menu. In particular, since the text of a message isn't selectable, the context menu is the only option for copying its contents. And copying the content of the message is something we are tempted to do to try to send the message again.
(Fractal 6, from Flathub, on Fedora 40.)