qmail is so nice:

  Hi. This is the qmail-send program at alden.berkeley.edu.
  I'm afraid I wasn't able to deliver your message to the following addresses.
  This is a permanent error; I've given up. Sorry it didn't work out.

  <jer@media.stupified.org>:
  Sorry, I couldn't find any host by that name. (#4.1.2)
  I'm not going to try again; this message has been in the queue too long.