linux – Blocking port 25 for a kvm virtual machine on the server

I need to know how to block the port 25 of a virtual machine on a KVM server with the help of ebtables.
The VM has the name of the interface viifv3035 on the server and brctl shows this:

# brctl show
bridge name bridge identifier interfaces activated by STP

viifbr0 8000.448a5b847b85 no eth0