Windows Backup creates an Event if backup was successful (you can find details
here). You could enable Information Event scanning and set up EMail-Alerts for this event ID, but this will cause a big load on your whole network and on your Lansweeper server as Information events will be collected from all computers.
Possibly it would be better to generate a script which searches for this event ID and gives back a result, i.e. on a file share. You could set up a regular
deployment schedule to deploy it on the relevant servers each day or each week.