if my email ever broke, i'd switch to a day planner
Email. As in messaging on the internet that predates the web browser itself. Before there was browsing, there was messaging. Why? Because it's just text, and that's the smallest, simplest data you can transfer.
I use email to organize my life, so I get all sorts of super nerdy when it comes to using it exactly the way I want. Very recently, I just did a major switch in how I use it.