If you want to completely disable the jetpack subsciptions module, here is how :
- Go to Jetpack → Dashboard and scroll to the bottom.
- Click Debug to open the “Jetpack Debugging Center.”
- Click the “Access the full list of Jetpack modules available on your site.” link at the bottom.
- Once you are on the page that lists, Jetpack modules, scroll down to “subscriptions” and deactivate it.
Alternatively,
Switch off “Allow users to subscribe to your posts and comments and receive notifications via email” at Jetpack > Settings > Discussion in your site’s Dashboard.
Recommended : How To Stop WordPress From Sending New Posts To Email Subscribers.