Export RSS fedds from Mac Mail

MacOS comes with a command line tool pubsub to access the RSS feeds.
Some interesting commands are:

• Get list of clients:
  pubsub list clients:
• Get list of RSS feeds from client com.apple.mail:
  pubsub list client com.apple.mail
• Get only the URLs:
  pubsub list client com.apple.mail | cut -f3

Update: use background for the commands