As long as it's addressed to a serviceman and not just the unit, it's OK for anyone to mail. Flat
rate boxes from the post office are great for this. You can pack baked goods, and then stuff it full of fillers like nuts or hard candy or socks or whatever---it can be as heavy as you can make it, same price. I left my bar cookies in 2 half sheet pieces and wrapped them together well, then filled my box with snack pack nuts and chewing gum and halloween packaged twizzlers and jolly ranchers and bubble gum and crystal lite individual packets. These filled the box up but didn't smash the baked goods---at least I hope they didn't. I used one of the bar cookie recipes from the Nestle site.
And you have to fill out a Customs Form with details of the contents.