By default, the customer notification template includes a link to disable notifications for a request - using the following variable: ${request.disable.notifications.url}. However, it is only possible to re-enable notifications via portal.

Many help desks rely exclusively on emails and customers don't sign up nor access the ticket via portal.

If a customer clicks to disable notifications, they'll stop receiving notifications and because they don't access the portal at all, they lose all contact with their request.

There should be a variable available on the customer notification template to (re)enable notifications for a request without the need to access the portal.