I stumble upon this all the time. It’s logged as an error, and it usually comes in bunches, looking like this:
So what to do about this. What is it?
Well, nothing. It’s a false alert if there ever was one. It’s basically saying that someone tried to access a website (Exchange website in this case) using an unsecure connection, when a secure connection is required. Http instead of https usually.
I did spend a while trying to figure it out a long time ago, but it wasn’t a easy to find anything, so to put it plainly:
Disregard! Nothing to see here.