1. Go to Marketing > System emails and pick the Client or Admin tab.
2. Click the email's card (or Edit).
3. In the window, under Configuration, you'll see a single Emails:<email name> value with Yes/No options. Click it, choose Yes (send) or No (do not send), and confirm.
4. The change is saved immediately and the card badge switches between Active and Inactive.

Important: in the current version this switch is account-wide, not per kitchen - even on a multi-kitchen account there is one shared on/off value for each email, so you cannot leave an email on for one kitchen and off for another. If the window instead says The settings of this email can't be changed, that email has no on/off switch at all in this version (in practice, every email currently listed on the page does have the switch).