Your interpretation of the current mail client behavior is accurate. In the upcoming mail client changes, the mail client will be able to background-load those

Your interpretation of the current mail client behavior is accurate. In the upcoming mail client changes, the mail client will be able to background-load those "unloaded images" through a proxy at Apple. We don't yet know how that new behavior will intersect with the "don't load images until i permit it" behavior that you have enabled today, but presumably they can coexist peacefully as two options (that I'll be expecting and checking for, later on in the beta cycles): "Background-load images when new mail arrives" Y/N "Use Apple's privacy protecting proxy to load images" Y/N