Steve,
I've been looking into this and I can find at least some evidence of you having been sent a few duplicates of this message because the Bellsouth mail server was receiving the message and then for some reason prematurely disconnecting and our mail server couldn't be sure delivery had occurred and so kept trying. For example:
Jan 31 07:53:30 localhost qmail: 1138690410.295490 starting delivery 2514987: msg 15581839 to remote sgelkins@bellsouth.net Jan 31 07:55:01 localhost qmail: 1138690501.253673 delivery 2514987: deferral: Connected_to_205.152.58.33_but_connection_died._Possible_duplicate! _(#4.4.2)/
However I'm only finding on the order of 20-30 of these with the specific Message-ID that you provided before. Also it seems like it should now have stopped about 9 hours ago (the times here are in UTC):
Feb 1 12:46:50 localhost qmail: 1138794410.078865 starting delivery 2575017: msg 15581839 to remote sgelkins@bellsouth.net Feb 1 12:46:51 localhost qmail: 1138794411.741594 delivery 2575017: success: 205.152.58.33_accepted_message./Remote_host_said:_250_Message_received:_20060201114651.GBIS25935.ibm04aec.bellsouth.net@box2.squeakfoundation.org/
This success should mean that repeated delivery should have stopped.
Is this the only repeated message you have gotten? If you are still getting messages could you check for any different message-ids? I'll be around on #squeak on irc.freenode.net for a while this afternoon (although I will be somewhat erratic after about 4PM US central time and completely gone by 5:45 or so).
Ken