I have always had my shirts delivered to my PO Box as I never know when I'll be home, but I just tried to order one and got a message that says "This item cannot be shipped to a PO Box. Either remove this item from your order or give us a new shipping address without a PO Box." Strangely, it only seems to apply to shirts in the Schadenfreude and Shirtstorm, group. I tried ordering shirts in other sections, Shirt of the Day and Top 20, and did not get this message. Is there a reason for this?