Milter-greylist

I'm running sendmail with milter-greylist for 10+ years without any
problems. Wanted to switch to postfix on a new machine and  find no
working way how to configure.
Is there somewhere a milter-greylist+postfix Howto?

Postfix main.cf:
# milter-greylist
# milter_default_action = accept
# milter_connect_macros = j
# milter_protocol = 6
smtpd_milters = unix:/var/spool/postfix/milter-greylist/milter-greylist.sock

root@mars:/etc/postfix# ls -al /var/spool/postfix/milter-greylist/
total 8
drwxr-xr-x  2 postfix postfix 4096 May  2 15:34 .
drwxr-xr-x 21 root    root    4096 Apr 29 17:43 ..
srw-rw----  1 postfix postfix    0 May  2 15:34 milter-greylist.sock


greylist.conf:
...
# For sendmail use the following two lines
# socket "/var/run/milter-greylist/milter-greylist.sock"
# user "smmsp"

# For Postfix uncomment the following two lines and comment out the
# sendmail ones above.
socket "/var/spool/postfix/milter-greylist/milter-greylist.sock" 660
#user "greylist"
user "postfix:postfix"
...


postfix tries to talk to milter-greylist but no success:
May  2 15:47:56 mars postfix/smtpd[4912]: warning: connect to Milter
service unix:/var/spool/postfix/milter-greylist/milter-greylist.sock: No
such file or directory

Any idea?

Thx,
Carsten