Since many customers who don't frequent these forums don't know that the final leg of DHL shipping is by the USPS, it would be a good idea to ask the customer if the shipping address being provided is served by USPS, when they choose the DHL shipping option.
Many people like myself use a Post Office box instead of a street side mailbox for security reasons. When I order something for delivery by private carrier, I give my street address, which USPS won't deliver to (at my request). When I order something for delivery by USPS, I give my PO Box address, which private carriers can't deliver to. I imagine there are many people out their in similar situations. I'm guessing that they see "DHL", and think to use their private carrier address, instead of their postal delivery address.
Just a suggestion.