Mountain Lion removes RSS functionality from both Mail and Safari. To facilitate the transfer of your feeds to another RSS reader, you can collect the feed URLs by running the following script in the ~/Library/Mail/V2/RSS directory of your latest backup.Go to:
~/Library/Mail/V2/RSS/ in your latest backup.
Run the following in Terminal:
find . -name "Info.plist" -exec grep -A 1 Feed {} \; | grep string | sed 's/^[^>]*>//' | sed 's/<[^>]*>$//'