DHL Express worldwide was a huge enterprise user of HP-UX some years ago, and probably still uses it today, because their investment would be too large to write

DHL Express worldwide was a huge enterprise user of HP-UX some years ago, and probably still uses it today, because their investment would be too large to write off, as JohnFen said in a sibling comment about another company. They had many of their business-critical custom enterprise apps running on HP-UX on many HP PA-RISC servers worldwide, at various locations.