If you still have installed vmm 0.3.x you have to proceed this step first:
    * upgrade your vmm installation to version 0.4-r41
If you have installed vmm 0.4/0.4-r41 you have to proceed this steps:
    * stop Postfix and Dovecot
    * backup/dump your database.
    * backup/dump your database!
    
    * start psql and connect to the appropriate database (ex. psql mailsys)
    * update the database: \i update_tables_0.4.x-0.5.pgsql
    * GRANT SELECT ON postfix_alias TO postfix;
                                       ^^^^^^^^ <- your Postfix db user
    * execute upgrade.sh
    * start Dovecot and Postfix
else
     * read INSTALL