During the runtime of your operating system, it's perfectly normal that some files cannot be accessed. It's usual nothing to worry about (though, they are exceptions of course - as with the recent Sober worm).
The Cleaner doesn't report the most common unaccessible files (such as the usual registry files, swap file etc) - because as I said, it's perfectly OK. I don't know what are those 3 files you mention - but they don't look dangerous (and they are certainly not related to the MiMail-I worm).
I would suggest not to worry about them, they're probably just a part of your OS (therefore, it may not be the best idea to delete them!).