One day my older Macbook Pro (which is now not in my hands) started asking for iCloud password with text "This Mac can't connect to iCloud because of a problem with firstname.lastname@example.org." but I kept postponing it. The device is running El Capitan.
The deal is I don't want the person who was the mac in their hands now (I'm not sure I had a log out after 5 minutes set to on) to read my messages and I was hoping that this would mean they simple would not receive them on the mac - because it kept asking for my iCloud password.
And a tiny subquestion #2 - can I check to see when was the device last logged in?