Ok, the second occurence of this just happened. Mailman stuffed the entire header into the body of the message, and the message started with a glob of text that looked like:

     <3CC18918.AFF46174@pointecom.net><007f01c1e889$52607020$d9ea79a5@VirginiaGrafton>
     <012b01c1e88c$6bd6f6c0$8900a8c0@carolina.rr.com>

Now, those look like message ids that were probably on the list before (at least, they're all from systems that would have posted to that list.) Does outlook express have a habit of doing a news-like "References" style header, like an in-reply-to or something, that collects messageid after message id? Because both times this happened, the message started with a blob of message ids. I wonder if the parser is blowing up on too many continuation headers?