This is an international site - so from where to where would be helpful.
One key thing to be concerned with is to make sure everything in the case is very, very secure. It would even be useful if the recipient were capable of checking and tightening things up before powering up. It may be a good idea (if you have the ability) to pack the empty space in the case with the super large bubble padding that Amazon currently uses. It would keep things like video cards from flopping around - but would also need to be removed before power up.
Safety is a concern - but that can be mitigated with insurance - be sure to insure the package.
Additional to safety is packing material. If the inside is loaded with the large bubble padding I mentioned above - then a 1-2 inch surounding the case with styrofoam would be a minimum suggestion.
Then custom fit cardboard and pleanty of packing tape and you should be ready to go.
USPS, UPS, FedEx are all good and reliable.