I was emailing my source my address, when I ran into a bit of trouble. I forgot my zip+4 so I went on usps.com and typed in the addy of the post office i'm going through and it gave me a zip+4. My source emailed me back and said he typed in my po box number and city/state into usps.com and got a slightly different zip. (the last four didgets were different). So I was just wondering if anyone knows why this might be happening. Thanks