Does anyone else find this error irritating?:
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 ..
Your Postfix configuration has the virtual_alias_domains option set to mydomain.com. This overrides the list of domains from the virtual_alias_maps option, and should be removed.
.. your system is not ready for use by Virtualmin.
I want to put my stuff where I want to put it, not where some control panel tells to me. And it's perfectly fine to put the domains behind that parameter, thats what it's for. Ok, I'll stop ranting now.