[courier-users] courier-imap is moving mails from new/ to cur/. how to stop that?

[The E. <mhe...@in...>]

I have the following problem:

I use courier-mta (the full package) in version 0.66.3-4 (as packaged in
ARCH Linux) with various clients (mainly roundcube webmail and k9mail
from my phone) as well as accessing the maildirs directly via mutt.

note that I have disabled the "mark as old" feature in mutt.

Now whenever one of the imap-clients accesses my account and checks for
new mails in all subfolders, the imap server will move ALL new mails
from the new/ subdirectories of the maildirs to the cur/ subdirectories.
This means that mutt subsequently doesn't consider these emails as "new"
any more but rather as "old but unread", which is not what I want.

courier-imap itself still considers the emails as "new", as can be seen
when accessing the same folder via imap through mutt. Then they will all
be "new".

I am quite certain that courier-imap is the culprit that is moving the
message since it's happening no matter which imap-client I am using,
whenever I access a folder (i.e. list its contents), all new mails get
moved to cur/.

I've checked the config files a few times but can't seem to find a
setting to stop that from happening.

What I want is for mail to stay "new" (not just as shown via the imap
server but also in local maildir terms) untill it is set to "read". No
"old but unread".

How do I get that?

Thanks.