I just received the following bounced mail:

This is a delivery status notification from %s,
running the Courier mail server, version 0.52.1.

The original message was received on %s
from %s

I love how the one bit of information that came through is the exact version of Courier that they’re running. Because that’s exactly what I need to pinpoint why %s isn’t getting mail that %s sent them at %s.