"False" Email Activity

We have an instance where a lead was sent to the sales team based on email activity, and upon the sales rep calling the lead, discovered that the person passed away several years ago.  Besides the fact that we have some old data that simply needs to be cleaned up, can anyone tell me why activity would show for a person's email that is no longer living?  My initial thought was that maybe his emails were being automatically forwarded to a colleague and that person was actually the one with the activity, but looking for additional reasons as well.  Thanks