[Dovecot] Log imap commands

[forumer at smartmobili.com]

I have added the following lines to dovecot 
configuration(/etc/dovecot/conf.d/10-master.conf) :

...

service pop3 {
   # Max. number of POP3 processes (connections)
   #process_limit = 1024
}

service postlogin {
   executable = script-login -d rawlog
   unix_listener postlogin {
   }
}

...


and I have created a folder dovecot.rawlog was shown below :

  root at vf-12345:/home/vmail/smartmobili.com/webguest# ls -la
...
drwxrwxrwx  2 vmail vmail   4096 2012-01-11 19:11 dovecot.rawlog/
-rw-------  1 vmail vmail  19002 2011-12-27 13:01 dovecot-uidlist
-rw-------  1 vmail vmail      8 2012-01-11 12:52 dovecot-uidvalidity
...


And after that I have restarted dovecot and logged in with the webguest 
account but cannot see any logs.
What am I doing wrong ?