to follow up on what Earl Hood said:
Your MUA screws up the References: header field. It also
does not include the message-ids of my messages.
Yes, it did. Dunno how, it's a normal flavor of Eudora.
Hope this one is fine...
Nope. What Eudora is doing is copying the first unfolded line of
In-Reply-To field value of the message being replied to into the
References field. Hence, if the message has other data in the
In-Reply-To field with the message-id, then the References can get
screwed up, and not even contain the referenced id. On top of that,
References is not being used properly. It does not set References as
defined by the RFC (cannot remember number) dealing with USENET
postings (where References come from). The most recent referenced id
should be added to the end of the References list, not the beginning.
However, see also the current drafts of the NNTPEXT working group
in IETF, also the USEFOR group, and the work of Jacob Palme on
mail/news harmonization if not covered in those.