[balac]

Surely if the servers are located in the US you cannot argue that it is really a foreign post office.

[ec429]

If some airmail stages through a US airport, does the US have the right to rifle through the mailbags on the plane?

[atakan_gurkan]

Not that I think this analogy holds, but I believe they would have the right, unless there is an international treaty that forbids them from doing so. That's what sovereignty is about. It is a privilege to use a US airport for this purpose, not a right.