[secant]

It's too long ago for me to remember the site's name but the subscription to it came when you signed up for a free Hotmail account back in the late 90s.

You would get an email each day that would take you to the site where you had to solve a reasonably cryptic whodunnit. I've never been good at these sorts of things but I would spend ages reading the story trying to solve the riddle. Pretty fun but years later I can't remember its name and I do miss it from time to time. It was a comfort to know these puzzles were being created and solved in the background but now is no more.