Don't risk mailing it from overseas. Smoke the weed thats there, and when you/ your friend gets back smoke the weed there.
Domestically is another thing. I worked at UPS for several years. I was a boxline sorter, and my job was to sort the packages coming off the Semis by address to get them to their proper UPS driver route and Van.
There were definitely some suspicious packages!
(UPS stands for United Pot Smokers btw..)
What I would do is seal it up real good in plastic. Surround it in coffee grounds ( a la Beverly Hills Cop ) throw in a couple other items like a book or T-shirt , and make sure the package won't accidentally open from handling.
Those packages get kicked and dropped quite frequently.
They have a sophisticated tracking system now, so use your Grandma's home address or some other address that is real.. say your neighbors
. use your dummy e-mail that you use for spam and internet trolling and not your real name.
(Kinda' like when Evander Holyfield got popped for getting steroids thru the mail and used an alias of Evan Fields
)
Voila'!
Your buddy on the other end will like more you for it.
UPS is pretty safe if you're not a total douchebag about it.