Klammer just works
Unlike some of its competitors, Klammer just works (in other words, it actually opens winmail.dat files and then opens the files contained in the winmail.dat files); and the price is very reasonable. The only reason I am giving it 4 stars rather than 5 stars is because it crashed when I tested it to see if could open an 18 megabyte winmail.dat file; and I suppose the developer could argue that opening an 18 MB file is pushing the program beyond any reasonable limit.
HWHW about
Klammer, v3.0