"subscribe by email": provide logged-in link

This is a feature (or how-to) request. I'd like the link to the post to set a logged-in cookie.
I'm working with a company that needs to grease the wheels for its users to start using the new internal blog more effectively. When the user gets a notification of a new post, it would be great if the link (to the post) would set a cookie to save them the trouble of needing to log in.

Also, I'd like to be able to specify the post category for which notifications are sent.