[Update: To be honest, I don't really know what this is. I'm out of my depth. But in any case, no harm in changing your password, particularly to a fresh and long one.]
Online there is a long list of stolen email addresses. They could have been hacked. If you find yours (like I did), you better change your password.
(Download the list. Open it in a pure text editor. It may take a long time to open it, it did even on my computer with a solid-state disk.)