If someone actually has somehow got your address through Minecraft without you sharing it, I would be impressed for lack of a better term. It is near impossible to get someone’s address through Minecraft. Did you click on any urls they sent you (if any). If you did, they may have your IP address and could use that to get your general location, but not your precise address. But even if someone claims to have your location. Do as Dutchyyy said and create a player safety report just to be safe. Also, what kind of postal card is it. If it is a business card or something, you could report them for advertising.
