Shipping iMac in original box

I have done exactly this with a 2010 21.5" i-Mac when I sold it after I purchased a new i-Mac. I did have and used all the original foam inserts and clear plastic wrap. It shipped fine and I got no negative comments on it's condition.

Yes, the original box is the ideal box to use. For added security, it would not hurt to double box it with some peanuts, foam or bubble wrap.