If they didn't slap DRM on it, you should be able to change the file extension to .prc and the mobi reader would read it fine -- if I understand how it works correctly, that is.
However, it sounds like they slapped their proprietary DRM on it, which would mean that it can only be read on your not-yet-arrived Kindle.
That's a
big deal if they're putting DRM on stuff
you send to
them for conversion. I know you have the original file so you still have access, but I can't see
any sane justification for DRMing the files sent to them for conversion!
