Please I did not understand how to configure postfix if I try to create a virtual server tells me:
Failed to create virtual server : No virtual domains file (virtual_alias_maps) was found in your Postfix configuration!
The status of your system is being checked to ensure that all enabled features are available, that the mail server is properly configured, and that quotas are active …
BIND DNS server is installed, and the system is configured to use it.
A problem was found with your Postfix canonical maps, used for outgoing address mapping : No map sources were found in the Postfix configuration
… your system is not ready for use by Virtualmin.
Always the same message … Sob 
virtualmin-base failed to install correctly on your system–this is the same as all of the other problems you’ve been reporting. There aren’t separate problems, even though they seem to be.
Run this:
rpm -e virtualmin-base
yum install virtualmin-base
(Note that I thought this problem was fixed on all platforms yesterday, but it actually didn’t get fixed on Fedora 7 until today, and possibly a couple of others.)
Ok now the result is this:
The status of your system is being checked to ensure that all enabled features are available, that the mail server is properly configured, and that quotas are active …
BIND DNS server is installed, and the system is configured to use it.
Mail server Postfix is installed and configured.
Apache is installed.
Webalizer is installed.
MySQL is installed and running.
Current logrotate configuration is not valid :
error: stat of /home/sito.net/logs/access_log failed: No such file or directory
. This must be fixed, or log file rotation will not be done.
… your system is not ready for use by Virtualmin.
But mail is not sent nor received
Dir in which I said I saw that the file acess_log exists and there are also log but I do not understand why say that there is