Please do not send emails to your customers. It is an annoying feature that should be discontinued. It is deprecated anyway. You only ever see complaints about it.
Your followers will get notified about devlogs you make and your paying customers will also get updates to the game page in their feed, even if you do not make a devlog. They can deactivate emails and ignore the https://itch.io/my-feed of course. That's also what no drm means. You cannot push updates, if the customer does not want them actively.
The Itch app does handle updates, but users can refuse.
People usually know, if a game is in development and probably will look for updates every now and then, regardles what you do.