I like to give my friends boxes of cookies for Christmas. How can I ship boxes to those living across the country or in neighboring countries without them getting damaged or going stale in transit? Would vacuum-sealing help? Do certain types of baked goods ship better than others? Should I use a certain type of box?
Cookie selection is key. You want to ship cookies that are going to stand up to the journey well.
Hard, dry cookies like biscotti or Mexican Wedding Cake cookies ship well.
Denser bar cookies, like brownies or blondies, packed well, should also stand up to shipping, and their rectangular shape makes it easier to fit them into the shipping container.
Moist, chewy cookies like Snickerdoodles or Chocolate Crinkles may dry out if the shipping time is extended, so only ship them to people you know can receive the shipment quickly.
Avoid filled cookies or those that are only at their peak for a day or so, like most sandwich cookies or French macarons (Coconut macaroons actually ship quite well).
Avoid any cookie requiring refrigeration.
Avoid cookies with small points (from cookie cutters) or delicate decorations which may break off during shipping.
Optionally, wrap pairs of cookies together back to back, in film wrap. This will help them stay whole, and provide a little extra padding.
Pack the cookies well in an airtight container, neither under nor overfilling it (perhaps using some loose crumpled food safe plastic or aluminum foil to fill any voids in the container, so that the cookies don't jumble around in the container.
Avoid mixing moist and dry cookies in the same container.
Use good cushioning such as bubble wrap or packing peanuts when you pack the cookie container into the shipping box.
Ship by the fastest means that isn't prohibitively expensive.
Do not include milk in the package.
I've had no complaints using two different methods of shipping:
The last few years, I've been using 9" round aluminium take-out containers ... but I put a few sheets of crumpled up waxed paper in the top to keep the cookies from bouncing around in the container. I don't recommend aluminum foil for this, as it won't bounce back after it's been crushed.
I also tend to use USPS priority mail (flat rate boxes). I've only once shipped cookies overseas (to Spain ... again, no complaints ... can't remember what class of mail I used, though. I think I also put the plates into gallon zip-top bags for that shipment.
And I should also state that all of the cookies tend to be of the firmer varieties. (shortbread, gingersnaps, peppermint candy canes, bar cookies, etc. If I have thin cookies, I'll stack them up on each other. I also tend to make smaller cookies (shortbread and bar cookies in 1" (2.5cm) squares, round cookies maybe 1.5" (~4cm) across, mostly so that people can have a couple rather than just one large cookie, but it also keeps the slenderness down which can affect breakage.
... and I've seen the results of the shipment via putting the take-out containers in checked baggage, and had no breakage.