Hello everyone,
I have now found a solution. In the Virtualmin preferences, the ASN plugin and the RelayCountry plugin are not activated.
This is simply because the corresponding GeoDB databases must be stored for both plugins.
To do this, you must first register with maxmind, if you have not already done so, and download them.
The databases are stored in a standard directory, which is searched by SpamAssassin by default.
This can be, for example,
/usr/share/GeoIP
The plugin is activated by an entry. I would do this in the file
/etc/spamassassin/init.pre
with the entries
loadplugin Mail::SpamAssassin::Plugin::ASN
loadplugin Mail::SpamAssassin::Plugin::RelayCountry
I wrote the configuration of the plugins in the file
/etc/spamassassin/local.cf
as this allows you to maintain the entries via the UI of Virtualmin or Webmin.
The default entries for both plugins are listed in the documentation and can be customized if necessary.
After the changes, the services would need to be restarted once.
There are many more plugins for SpamAssassin that can be used to further minimize the number of spam emails that get through. These are just two of them.