First, the post office is not a company but a government service so it can LOSE money and that's fine. Second, they don't they make a little on local delivery and bulk and lose a little on long distance. It's not rocket surgery.
I don't think it's fine we're subsidizing domestic shipping rates to mail to foreign citizens on foreign soil, save maybe a few rare exceptions like they're acting in an official capacity on behalf of the US.
Are American citizens not entitled to send mail to other citizens overseas? I would argue that most mail that is sent abroad is between American citizens and their families (military care packages, Xmas cards for expats, etc).
