Libra Esva has no built in capabilities of geo-blocking email, thought there is an external free service that can be used as RBL in Esva.
The service is the following: http://spameatingmonkey.com/geobl/usage.html
Using this service you can generate a RBL server name that will allow your server to block mail originating from any country, continent or combination thereof.
For example, to block all mail originating from Italy you can use the following RBL server:
Add your custom RBL under menù System->Relay->RBL Filtering and press Apply Settings.
If, for example, you would like to block all of Asia, the United States and Brazil then you would use the blocking clause of “basia_us_br” and your RBL would look like: