Hi,
In Odoo 18, you don’t need to delete the email templates to stop customer notifications; you can simply disable or unlink them from the automated workflows. Odoo sends customer emails using predefined templates linked to actions such as confirming a quotation, validating a delivery, or posting an invoice.
The safest way is to go into Settings → Technical → Email → Templates (you may need to enable Developer Mode). There you will see templates like Sales Order: Confirmation Email, Invoice: Send by email, or Delivery: Shipped Notification. Instead of deleting them, you can either deactivate them by unchecking the Active field, or remove their association with the corresponding workflow rule or action.
Another approach is to check the Automated Actions / Mail Rules in Technical settings. Many of these are triggered by activities like "Order Confirmed" or "Delivery Validated". You can edit these rules and unlink the email template so the system does not send out notifications.
This way, Odoo will still allow you to manage orders and documents internally, but no automatic customer emails will go out. If in the future you want to re-enable them, you can simply re-activate the templates or re-link them to the workflows.
Hope it helps