go down 49 like you are going to URE and go past 109 then when you get to the next MAJOR intersection (about 15-20 mins past 109 IIRC) make a left. head down a few miles and you will see it on the right. tons of big trucks and a big sign
The "P.O." box on their site is their address. That's just ol school.
Our address used to be box 8 rural route 3...
Anyway the new loundon post office is on white street not hwy 52, and Galloways's is on 52, so I am assuming the addy is 8 hwy 52 new loundon...
But like the others said take 49 to 52 and you can not miss it. If I remember correctly there is still a sign at this intersection.