Dear Princess Celestia:
I honestly don't see why ponies are getting all worked up over the government sifting through their mail. I mean, it's not like anypony is interesting enough for us to spend our days spying on every little thing they do. Seriously, why should they care if we read every letter about how they watched their kittens doing cute things with string? Do they seriously think that we're going to bother looking into that?
With that said, I'm sure there are things that may be a bit more justifiable. For example, I'm sure some ponies may write long, graphic depictions of all the various things that they experienced when having sex. Honestly, if I was sending that through the mail, I'd be worried. Hell, you know how I freaked out when Luna tried to invade my wet dreams. Of course, there is no way I would send that sort of information through the mail anyway. And honestly, anypony dumb enough to mail that deserves to be spied on.
What does that leave? Sensitive information, apparently. But what counts as “sensitive”? Does it mean that information has feelings and empathy and stuff? Or it it pressurized and ready to explode at the slightest prodding?
Am I just mocking you at this point?
Maybe you just mean news about how somepony's gonna bomb the castle or something. Yeah, but are terrorists really dumb enough to not realize their letters may be intercepted? I mean, I'm pretty sure they have some sort of secret code to describe how they want their missions to be carried out without alerting the authorities. How else can you explain my fifth birthday party?
So, in short, I don't see why ponies care about this, but I also don't see how spying on ponies' mail is going to solve anything.
Your irritated fellow Princess, Twilight Sparkle.
P.S.: If you find anything erotic, have it sent to me for, ah, analysis.
P.P.S.: I am intrigued by this “Flash Sentry” pony. If he is captured, I wish to deal with him myself.