[Exim] Using exim with mailman

Trying to get exim to work with mailman and hit a problem.

What I send a message to the test list I get ...

A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error. The following address(es) failed:

  pipe to |/var/mailman/mail/wrapper post testmailman
    generated by testmailman@???
    Child process of address_pipe transport returned 2 from command:
    /var/mailman/mail/wrapper

Anyone know that this means?