Diane Barlow Close wrote,
| Personally I think this type of problem could be solved if their error
| messages were a bit more specific -- after all, the mail is being
| _forwarded_ from JBlow@foo.edu; shouldn't the error message go back
| there too?
Absolutely it should. It was the person using JBlow@foo.edu who put the
bad forwarding address onto your list's mailings by directing his or her
mail there, so it is JBlow@foo.edu who has control over it. Mail that is
forwarded that way should be bounced back to the forwarder.