Can I see the URL of an RSS feed on Apple Mail 4.5?
Once an RSS feed is added to Mail, you cannot see the URL it retrieves anywhere within Mail :(

There does not appear to be any way you can read the configuration using Applescript, looking at the dictionary, the RSS feeds are not accessible either as a distinct entity type or as a Mailbox type.

The only place I can find this information is in ~/Library/Mail/RSS

Each feed is a folder with an .rssmbox extension and inside the folder, the Info.plist contains the URL of the feed.

edit: change reponse re: applescript after further investigation