These reusable postcards are meant for play, so I laminated them to use again and again. They work great with washable crayons, markers, and dry-erase pens. (Crayons are the least messy because they won't rub off on hands or clothes.)
Abe is too little to write letters, but he's starting to recognize a few...and since we don't encounter his name too often in books, I figure this is a good way for him to see it spelled out.
To make your own reusable postcards, download my scenic postcards PDF here. Print them out on cardstock or heavy paper, and cut them apart before laminating.
I'm sure you could send these through the mail if you write on them with a Sharpie. (You can erase Sharpie marks from plastic with a little bit of rubbing alcohol.) Just make sure to add a real stamp!