Here's a better description of what we would like:
When you click on a link in an email notification to a post in a category that's not viewable by the public and you're not logged in, you get a 404 error message. Make a change so that the person receives a message saying "This category is restricted and cannot be viewed by the public. Please log in." Then, after the user logs in, they should be taken to the link they clicked on.

Hi there,

You can enabled this settings here http://take.ms/uqDTX and you will be re-directed to your frontpage if not logged in. I have enabled them for you and it should works as it should now.

Please give it a check and see how it goes.