I've noticed that with the new output plugin calibre pretends to be kindlegen by setting the EXTH records 204-207.
Unless this is necessary for some features to work (which would surprise me), I'd lobby to either use a unique value for record 204 which would identify calibre and set records 205-207 according to the current calibre version or, as we can't predict which values for record 204 amazon will use in the future and the calibre version is already available in the contributor record, don't set the records 204-207 at all.
As the calibre output can't be 100% identical to the kindlegen, no matter how much effort we put into it, pretending that kindlegen created the mobi file might break tools which depend on the kindlegen version to be correct.
I've also seen that calibre has a kindlegen option which when enabled uses the kindlegen binary to create the mobi file instead of the calibre python code.
It looks like a debugging option and I couldn't find a way to enable it in the calibre gui, but as this option is the best of both worlds for some users, having the epub conversion done by calibre, which is far superior than the epub conversion from kindlegen, together with a mobi binary created by the official amazon tool kindlegen, it would be great if this would be a user selectable option on the mobi output option screen of the gui.
With that option the AZW Conversion Output Plugin (http://www.mobileread.com/forums/sho...80&postcount=1
) should be obsolete, too.