KloxoMR does not support DKIM straight out of the box. The reason is qmail-toaster does not either.
Using a few different methods and a fix of an old perl script I have DKIM firing properly on all three of my servers.
I was testing the load under a lot of out bound mail but my server didn't appear to have any problems handling bulk mailing - cpu was alittle higher than normal, but not red zone
I will place the files on my server for download (i did not write them, they have been around for years, I just modified them to use KloxoMR default keys and DNS).
It really is simple. I will add a tutorial to tips and tricks very soon.