Notification emails are sent even when email notification is "Disabled"

User Story

As a user of our own gitlab.medstrat.com server who has "Profile Settings > Notifications > Notification level" set to "Disabled", I noticed that I am still receiving emails from gitlab.medstrat.com though I do not want to be receiving them, so that I only need to check Slack for notifications from GitLab instead.

Elaboration

I want to only be notified via our Slack integration and not via email. Using GitLab 8.2 on-premise at the moment and because I am still getting emails, this is not possible. Any ideas?