[Mailman-Users] Mail header weirdness, please respond.

Since our upgrade to MM2.1, the Cc: field of messages sent to the list,
if it has addresses in it, is altered to multiple cc: headers. For
example, Cc: user at dom.ain, user2 at dom.ain, user3 at dom.ain when expanded and
resent by mailman becomes, on seperate lines:

cc: user at dom.ain
cc: user2 at dom.ain
cc: user3 at dom.ain

Is it possible that this is expected behavior? Is there a reason for
this? Is it a configuration issue on my part? FWIW, I'm running
Mailman2.1 on Solaris 6 with Exim 3.36.

Thanks in advance.