[Dovecot] Mail root to root and permissions problem

[Antonello Onida]

Hi all!
I got a Debian with postfix-dovecot-spamassassin.

I got a non perfect installation: when an internal mail has been sent i 
got this error:
<error>
ex: from root@*     to root@*.
Command output: Can't open log file /var/log/dovecot.log: Permission denied
</error>
Operations like "dovecot: 2009-12-15 11:17:24 Warning: Killed with 
signal 15" are writen.
It's a permission problem: dovecot.log is owned by "root" and grupped by 
"adm" (chmodded 640).
Where is the problem? I'm really blind now!

Tx 4 suggestions!
Bye, Antonello