iTunes not recognizing RSS Feed enclosures as valid podcast episodes?

iTunes is not recognizing the enclosures in our RSS feed as podcast episodes. We're using Feedburner to add iTunes-specific tags to the feed, but iTunes has the problem with the original feed as well.

Here's our original RSS feed:

http://www.esvbible.org/devotions/rss/chronological/

Here's our Feedburnerized feed:

http://feeds.feedburner.com/ESV-Chronological

Here's the podcast page on Apple's site:

http://itunes.apple.com/us/podcast/esv-chronological/i开发者_StackOverflow社区d301024126

The enclosures are still there, with the appropriate type. Feedburner has changed the length of the enclosure from the empty string to "0", which after checking the spec is technically correct. What am I missing?

Turns out, iTunes completely ignores the MIME type, and is dependent upon the .mp3 file extension in the URL. Adding the extension fixes the feed.