Here is the scenario you or a client have a remote machine that was installed as a standard/default minimal Centos 6.x machine on a single disk with LVM for whatever reason. Often many people do not know how to install it to a RAID array so it is common to have this problem and why reinstall if you don't need to? In some cases on a remote system you can't easily reinstall without physical or KVM access.
So in this case you add a second physical or disk or already ha........
Virtualmin Postfix Error:
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 ..
A problem was found with your Postfix virtual maps : No map sources were found in the Postfix configuration
.. your system is not ready for use by Virtualmin.