[Dovecot] Dovecot DELIVER

[Bruce Bodger]

Tried today to use Dovecot's DELIVER LDA.
I'm running Postfix 2.1.5. I simply added the line...

mailbox_command = /usr/local/libexec/dovecot/deliver

to main.cf and made no other changes.  First email resulted in this  
in mail.log:

May 16 06:29:56 G518X2 deliver(bb): open(/var/mail/bb.lock) failed:  
Permission denied
May 16 06:29:56 G518X2 deliver(bb): file_lock_dotlock() failed with  
mbox file /var/mail/bb: Permission denied
May 16 06:29:56 G518X2 deliver(bb):  
msgid=<7e0d81210705160329n76c784d1m84571d33af7389b4 at mail.gmail.com>:  
save failed to INBOX
May 16 06:29:56 G518X2 deliver(bb): open(/var/mail/bb.lock) failed:  
Permission denied
May 16 06:29:56 G518X2 deliver(bb): file_lock_dotlock() failed with  
mbox file /var/mail/bb: Permission denied

Permissions on all inbox files in /var/mail was 600. Owned by  
<username>:mail  I tried changing to 660 but got the same result.
Dovecot user is member of mail group.

Any ideas?

Thanks in advance.