Post / Comment E-mail Notification All Subscribers

I’ve seen this topic discussed in other forums but not this one. I’m looking for a simple plug in that will notify all subscribers of any new posts or comments. No body or comment needed. Just a subject line that say’s something like “Mike W has posted a comment on Joe B’s home page”. No option for subscribers to install, uninstall, or modify the notice (they can delete it if they don’t want it). Set up by the administrator automatically with all existing subscribers and or new subscribers.

I’ve seen some HTML code examples but don’t have enough experience with that to know how or where to modify functions.php