On Tue, 22 Aug 2000, Pete Weiss wrote:

+ >> <W> MESSAGE-ID field duplicated. Last occurrence was retained.
+ >>
+ >> I have seen this error before, and have not been able to determine what is
+ >>  causing it?
+
+ I think that particular Eudora problem is fixed in 4.2+. [I think it
+ resulted by multiple compose windows being opened at the same time.]

Over here the probleem seemed to be caused by multiple edits of a draft
message, for example people writing trip-reports on their laptop directly
in a Eudora composition window and doing a few saves before actually
sending the message. Every save resulted in another instance of the
Message-ID. I can't reproduce that in 4.3.x so it indeed looks like it's
fixed (although the release notes of the 4.2+ versions do not mention it).

Xander