Do you track USPS packages anonymously? If so, how? If not, why?
In my mind checking a domestic package through a proxy could potentially raise some flags, especially if the IP is foreign. On the other hand, if you check the package from an IP that can be traced back to you, then you can't plead ignorance if need be.
There is a rumor that tracking through TOR raises a red flag and alerts LE but as far as I know no one has ever proven that this is the case. I have tracked through TOR before and my packages always show up no problem.