The Kindle whitepaper is out of date. In particular, it seems that Amazon does not accept Calibre-created.mobi files - .mobi files created by converting from .epub to .mobi in Calibre - and insists on using Kindlegen to create .mobi files. In my experience, however, Calibre does a better job of converting from .epub to .mobi than Kindlegen, and I do not know why .mobi files created by Calibre are unacceptable.
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