Block all emails from the domains from which they come. You put yourself on a sucker list, and while you can’t get off the list (they will likely sell your name and email to other campaigns in the future) you can block the sender so they never reach your inbox. Repeat for each purchaser.
Bingo! Log into your web email server and set up the block out there. The emails will never download to your client machine, but be trapped out there.