marking a message as "read"

[Cameron Simpson]

I've some confusion about "read" and "unread" versus "old" and "new".

There are status flags for new and old. Unread messages seem to be new, 
but if I read a message it doesn't acquire an "(O)ld" flag, though it 
loses its "(N)ew" flag.

I've skimmed the manual, and i can't see what the criteria are for 
considering a message New or Old.

What I'm trying to resolve is this:

When I enter a mailbox I want to collapse all the read threads. However, 
in a mailing list box my own messages land in the box, and they're both 
New and Unread. So before i collapse the threads-with-no-unread I want 
to mark all my own messages as read.

It's easy to find these messages, but I can't see how to mark them as 
"read". I can mark threads and subthreads as read, but not individual 
messages.

Suggestions anyone?

Cheers,
Cameron Simpson <cs at cskk.id.au>