Hello Emanuele!
With this setting enabled, all HTTP SmarterTrack URLs will be redirected over HTTPS. This improves SmarterTrack security by allowing all traffic to be encrypted, and it doesn't rely on the user specifying HTTPS.
Prior to enabling this setting, SmarterTrack must be set up as a site in IIS and have a valid SSL certificate in place for the SmarterTrack site. (Note that this option is not available for those using the hosted SmarterTrack helpdesk, as a secure connection is already in place on the SmarterTools servers.)
Hope this helps!