Global Express to Spain costs quite a bit more- 17 or 18 dollars. But there are no sticky fingers getting inside that envelope. If you've seen one, you know what I mean. It also provides tracking, though sometimes it doesn't work outside the US (the point of that would be?)

At any rate, it's a totally legit way to send important documents abroad. I received replacements for stolen credit cards once this way. It also only take a couple of days. When I sent cash, I used this method. If you have $$ to spare and want to speed things up, this is a reliable way to do it.