Here's what people have said about working and interviewing at DHL.
Work wear or smart casual
Dhl, the location I work at, has a recruitment office. They sit you down get all the paperwork and they do a drug test, background check (cause it is the airport), then they do a lift test. You're on your feet and lifting heavy stuff so they ask you to lift a 50 pound box, to make sure you do it appropriately. They interview you and write down more information. It was simple and casual.