Cannot send local mail with postfix from packages.

[Marcus Lindemann <mli_(_at_)_shebang_(_dot_)_de>]

Hi,
when I send mail to a local user like

obelix(ttyp1)> mail test
Subject: Test2
This is a nice test
.
EOT

I immediately get
postdrop: warning: mail_queue_enter: create file maildrop/868868.18121: 
Permission denied

I googled around, but didn't find anything that enlightened me.

Permissions on maildrop:
obelix(ttyp0)> sudo ls -ld /var/spool/postfix/maildrop/
drwx-wx---  2 postfix  postdrop  512 Nov 12 18:17 
/var/spool/postfix/maildrop/

Permissions on postdrop:
obelix(ttyp0)> ls -l `which postdrop`
-rwxr-sr-x  1 root  postdrop  73656 Feb 29  2004 /usr/sbin/postdrop

however:
obelix(ttyp0)> ps -aux -Ogid,group,rgid,rgroup | grep postdrop
mli       9342  0.0  2.3   180   728 p0- S      5:59PM    0:11.91 
postdrop -r         10 users       10 users
mli      12173  0.0  3.3   172  1084 p0- S     10:20PM    0:02.31 
postdrop -r         10 users       10 users
mli      21290  0.0  0.0   960     4 p0  R+    11:24PM    0:00.00 grep 
postdrop (b    10 users       10 users
mli      18121  0.0  3.4   212  1088 p1- S     10:16PM    0:02.41 
postdrop -r         10 users       10 users
mli      26240  0.0  2.3   192   744 p2- S      6:20PM    0:11.63 
postdrop -r         10 users       10 users

I would have expected to see the postdrop group in the gid and group 
columns. Any ideas of what might be wrong?

BR
Marcus