This problem still has not been solved. Has anyone had this problem occur? For clarification, here are some "screenshots" copy-and-pasted from a term ..
-- Mutt: Mailboxes 
1 11664 Oct 19 13:43 N =default
2 0 Sep 11 11:08 =duplicates
3 0 Oct 19 13:38 =junk
4 0 Oct 19 07:20 =spam
q:Exit c:Chdir m:Mask ?:Help
In the above, one can see that the "default" mailbox (where the incoming mail goes) is marked with an "N", indicating that there are new mails to be read.
Now, we move the cursor to the "default" mailbox and press enter and we see this:
- 0 =default 0 Del 0 Msgs 4 11K (all)
1 + Oct04 firstname.lastname@example.org You have been added to this usergroup
2 + Oct08 gohomeproductio GHP vs Dylan / GHP DJMix Oct 2007
3 F Oct12 To xxxxx, xxxxx Keeping in touch
4 + Oct15 noreply@letters NaNoWriMo loves lokken
q:Quit d:Del u:Undel s:Save m:Mail r:Reply g:Group ?:Help
Note that in the above, certain portions of some of the addresses have been "x"-ed out. That is the only alteration of the "screenshot" above.
More importantly, note that none of the four messages are marked as new/unread.
Mutt is indicating that messages are unread when all have been read. Mutt is wrong,
What command is the one that forces mutt to realize that all the mail is old, already read, not new?