> many mail server admins of large organizations don’t even look at these email rejections to take any action Because, sadly, it's trivial to forge the return

> many mail server admins of large organizations don’t even look at these email rejections to take any action Because, sadly, it's trivial to forge the return address and generate (many!) rejections to places that didn't send the email in the first place. (I've only got a tiny email server and I largely stopped caring about bounce messages a decade ago for this very reason. I can't imagine the volume Gmail or Hotmail get.) e.g. https://www.altospam.com/en/news/bounce-the-mail-bounce-attack/ https://www.altospam.com/en/news/bounce-the-mail-bounce-atta...