Within Teamwork Desk, you can disable happiness ratings for individual inboxes.

Note: Disabling happiness ratings for one inbox will not disable it for other inboxes.

Click your profile icon to the top right of the main navigation bar and select Settings.

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In the settings area, go to the Inboxes tab and select the inbox you want to edit.

Once you have chosen an inbox, select the Edit Inbox option in the left navigation pane.

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Toggle off the Happiness Rating option.

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For more information, see: Enabling Happiness Ratings