How did fedex know where I live

I had a package sent to my PO BOX. The sender used FedEx. I never gave the sender my physical address. Some how fedex managed to get my physical address and send the package to it instead of the PO BOX. How did they do this. What kind of magic are they using. I thought FedEx SmartPost only go to the post office. Did the post office give them my physical address?