You named your server the same exact name as a domain you are hosting virtual mail for. You shouldn’t do that.
This is covered in the docs (linked from the download page under the link “fully qualified domain name”):
Fully qualified domain name
If your system does not have a fully qualified domain name (FQDN), the installer will stop and ask you to choose one. This is mandatory because many services rely on having a fully qualified domain name in order to function. Mail, in particular, but some Apache configurations and many of the Virtualmin-created configuration files, also require a valid fully qualified domain name to function correctly. A fully qualified domain name is one of the form “srv1.virtualmin.com”, or simply “virtualmin.com” (but do not use a name you’ll be hosting in Virtualmin). We recommend you choose a name that is not one for which you will be receiving mail, in order to simplify later configuration. A good choice is to use a name server designator, such as “ns1.virtualmin.com”. Some customers also choose something like “host1.virtualmin.com” or “primary.virtualmin.com”. Any of these would be valid and would satisfy the install script and the services that rely on this option. The install script will add this name to /etc/hosts, which will satisfy all local services. It is even better if this name resolves correctly when looked up from outside of the system–this requires the name be added to your DNS zone for the second level domain. If the Virtualmin server you are installing will be the authoritative name server for this zone, you can later use Webmin to add a record for this name to the zone.