You couldnt mail it pre-planted for sure. Double box the glass unit, ship the other parts separately as a kit. Its going to be expensive to ship soil, gravel, etc.

Alas, Chaz is dead on. Piecemeal is the only way you could ship it. Otherwise, you pretty much need to wait until you go for a visit and take it along.

If the state is too far away to drive, if you cannot each drive halfway and do the transfer personally, if this terrarium is THAT important that you cannot give them instructions on how to make their own, you really MUST send this to your family member, and you are still willing to potentially lose the terrarium....

Check with the postal service to see if there are regulations with shipping live plants. If not, then fill the open space inside with packing peanuts to help the plants from moving around. Use plenty of packing material around the terr. inside the box so it does not move around at all. Perhaps even put some sort of bracing/stiff styrofoam around the entire thing, or fill the space between the terr. and the box with expanding foam for extra assurance it does not move inside the box. Definitely use sturdy box, or even double box it.

Take a picture of it before you box it up, and include the picture with the shipment, so the receiver knows what it was supposed to look like.

Mark the box a LOT with FRAGILE, THIS SIDE UP, LIVE PLANTS, and ship via the postal service. Glass and soil are heavy, so expect to pay a lot.

I think the postal service is the only carrier that will truly pay attention to THIS SIDE UP/FRAGILE, etc. But even then you are taking a chance.

Good luck!