Question Author
bert_h: If the US set up a base on the Moon, it would be US territory, much the same as Puerto Rico, The Marshall Islands or American Samoa, and all these places have US zipcodes. And perhaps what I should have said is that putting the zipcode on mail within the US - or its overseas territories - does facilitate the process. Mail without zipcodes arrives more slowly.
grasscarp: Well it could be Lost In Space...
Zacs-Master: Whooo-hooo hwooo, hooo-whooo-wooo