From the Adobe Digital Editions blog:
Today, we’re posting a how-to guide that explains how to convert eBooks authored using Adobe InDesign for compatibility with the Amazon Kindle and the Kindle Store. Because Amazon uses their proprietary AZW format, the Kindle doesn’t natively support the open EPUB standard. However, with a bit of open source software, it’s fairly easy to convert the EPUB files exported with InDesign into the Amazon-compatible MOBI format.
Converting InDesign documents for Kindle compatibility requires the following steps:
1. Export InDesign document to EPUB
2. Convert EPUB to Amazon-compatible MOBI format
3. Preview on Kindle device (optional)
4. Upload to Amazon store
For complete details, check out the Adobe InDesign to Amazon Kindle Store white paper