Mutt does not show new mail (because of maildir format?)

Hi,

I have been using mutt for a long time, then I changed to Clawsmail
(although mutt was very good...)

Now, I use mutt again occasionally, when I log into my computer via SSH.
The only thing that annoys me is that mutt does not show new mail as
"New", i.e. new mail appears in my mailboxes, but is not marked as
"New". What could be the cause of this? I use the Maildir format.
Clawsmail does not have that problem (but it is not running when I use
mutt.) I don't have anything like biff that could change the access
time.

I attach my muttrc.

Any hint would be appreciated.

Greetings,
Christian


My .muttrc:
---------------------------------------------------
source ~/.muttgpg
set mbox_type=Maildir
set folder = "~/Mail"
set mask="!^\\.[^.]"
set mbox = "~/Mail"
set record = "+sent"
set postponed = "+queue"
set spoolfile="~/Mail"
set editor = /usr/bin/vim
set move = yes
set delete = yes
set include = yes
set from="christian_obst@gmx.de"
set envelope_from_address="christian_obst@gmx.de"
mailboxes `echo -n "+ "; find ~/Mail -type d -name "*" -printf "+'%f' "`
color header brightred black "^Subject:"
color header brightred black "^From:"
color header brightred black "^To:"

bind pager <up> previous-line
bind pager <down> next-line
macro index <tab> '<change-folder><enter>'
macro index <esc>m '<change-folder>=inbox<enter>'

set beep = no

ignore *
unignore from: date subject to cc reply-to user-agent sender x-mailer