Originally Posted by tompe
You can probably test that by doing "mobi2mobi --savecover cover --savethumb thumb file.mobi" and see if the cover and thunb files are saved. They will only be saved if the file is a real MobiPocket file where the cover and thumb has been set in the correct way.
The original file has no picture so I could not test it. When I added the cover (selecting all three option) it dit not show up in mobireader. When I used mobi2mobi with --savethumb, the correct thumbfile was saved. So it was in the correct format. Just to be sure I used this file as input for a second run with a new cover. No luck