>>>>> "ZSH" == Shenghuo ZHU <zsh@cs.rochester.edu> writes:

Jack> * Message doesn't quite understand mail saved before I upgraded
Jack> to 20.3.  When I reply to older mail, message is unable to find
Jack> the author and subject.  The summary buffer displays this
Jack> information with no problem.

ZSH> Weird. If possible, could you send a (encoded) sample?

Sure, I can try.  The problem is completely solved if I do
(setq nnmail-file-coding-system 'raw-text-dos)

But the example is pretty straightforward.  With this value set to 'binary,
my summary buffer looks normal. As shown in the enclosed ex_summary.txt.
(All of these messages happen to have come before I moved to emacs-20.3.1.)
When I hit reply on a message, the message buffer looks like
ex_message1.txt.  If I change nnmail-file-coding-system to 'raw-text-dos
and reply to the same message, the message buffer looks correct as shown in
ex_message2.txt.  For this to work I must select a different message and
then reselect the first message for the nnmail-file-coding-system to take
effect when it reads that file.  (I am working in the nnml back end.)

I have also set
(setq nnheader-file-coding-system 'no-conversion)