Within Teamwork Desk, you can set a variable to include the ticket ID in a canned response.
To enable this, click your profile icon to the top right of the navigation bar and select Settings.
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Go to the Inboxes subsection of the settings area and select the relevant inbox.
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In the inbox details view, select Canned Responses from the left navigation pane.
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You can edit an existing canned response or create a new one by selecting the green Add Canned Response option to the top right of the screen.
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In the canned response modal, select the variable option from the editor toolbar.
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Select Ticket - ID from the dropdown menu of variable options.
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The variable will then be inserted into the body of the auto reply, you can position this anywhere within the reply area.
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For more information, see: Using Variables