Will definitely read up on those concerns. Thank you so much for the resources and for preventing us from getting sleep at night from now on.
;-)
Yes, and that's exactly what spammers do. They know better than to send the same message more than once, but they certainly won't abandon an address they know to be valid (no bounce).
The first might say, "Our automated analysis tool has detected that your computer has been infected. Click this link for a repair."
The second might say, "We're sorry -- your bank has reported a hacking attempt and we need you to change your password. Please enter your login ID and your old and new password."
The third might say, "Is your wife no longer happy? Try our miracle ..." (use your imagination)
Spammers might be intellectually challenged people, but they're not perfectly stupid, on the ground that nothing is perfect.