[otrs] Customer Notification on Owner Change

Hi, I would like to send out an email to the customer if the supporter gets owner of the ticket. I found some manuals, but they don't seem to work. What I do: * Admin -> Notifications (Event) * Create a new one ** Name: Foo ** Recipient groups: Customer ** Event: TicketOwnerUpdate ** Subject: Bar ** Text: Blah Blah ** Notification article type: email-notification-ext (this was the preset) ** Validity: valid ** Comment: Blah Blah But it doesn't seem to work. If I send a test to our helpdesk and close this ticket (as agent in the webgui), I'm getting no email. Regards Karsten