My first thought as well: how does one quietly reject email? Skimmed the comments and clearly it's not quietly. Saved a click...

It's quiet only if the server accepts it and then deletes it on their end without notifying the sender, but if your mail provider shreds your mail that's then also your provider's responsibility and not the sender's

Replying to all inbound messages with a bounce is an old idea. The theory was that legitimate senders would validate their address and get added to a white list. The scheme didn't work for the same reason captchas don't work.