title: Best Strategies for preventing addresses with PO Boxes?
body: <p>I have a client which is shipping via UPS, and therefore cannot deliver to Post Office boxes. I would like to be able to validate customer address fields in order to prevent them from entering addresses which include a PO box. It would be best if this were implemented as a regex so that I could use a client-side regex validation control (ASP.NET).</p>
  
  <p>I realize there's probably no way to get a 100% detection rate, I'm just looking for something that will work most of the time.</p>