As far as I can remember, I’ve never enabled Microsoft Cortana nor engaged with it in any way. 
But out of the blue this morning it sends me the email below that, among other things, says I have a task I need to take care of.

This particular "task" was an email reply I sent to my wife, so the only way Cortana would know about this is if it read my email.  Some may view this is handy; I view it as creepy.

HAL: “Dave, I think you really should move those boxes now.”