Postfix permissions.

[Dom Latter]

Got a broken postfix.  I get this error in mail.log:

Jun 22 17:21:08 hostname postfix/virtual[2377]: warning: maildir access 
problem for UID/GID=5000/5000: create maildir file 
/var/mail/vhosts/domain.com/dom.latter/tmp/1245687668.P2377.hostname: 
Permission denied

(hostname and domain name changed).

hostname:/var/mail/vhosts/domain.com/dom.latter# ls -l
total 12
drwxr-sr-x 2 vmail vmail 4096 2009-06-22 17:02 cur
drwxr-sr-x 2 vmail vmail 4096 2009-06-22 17:02 new
drwxr-sr-x 2 vmail vmail 4096 2009-06-22 17:02 tmp

in /etc/passwd
vmail:x:5000:5000:::/bin/false

in /etc/group
vmail:x:5000:

Thing is I have a working postfix on another machine and the setup is
(almost) identical (in fact I'm using my setup notes from the other
machine as I go along).

Any ideas?