avoiding duplicate messages with multiple lists

Hi,

Say I have three smartlist lists on the same host.  I send a single  
message to all three lists:

    To: listA, listB, listC

If all three lists contain the same subscriber, that person gets  
three copies of the message.  All three copies have the same  
(original) Message-ID, but different Resent-Message-IDs.

Is there any way to cause that person to only get one copy of the  
message instead of three?

The mail server is Mailman on MacOS 10.4, in case that's relevant.

Thanks,

--
Jamie Zawinski       [email protected]                  http://www.jwz.org/
                     [email protected]      http://www.dnalounge.com/
                                          http://jwz.livejournal.com/