I was getting a bunch of emails purportedly from someone I know whose email account had been stolen or hacked. The emails were going straight to the spam folder. I was checking the spam folder and purging it regularly without opening the suspect emails. The faster I purged them, the faster they came. I finally just left them in there and let them be deleted automatically by gmail after 30 days. The emails stopped. Evidently, they were able to tell that there was someone on the other end deleting them unopened.
Wow! That’s scary!