Related article: Send to Case - Overview
When you use the desktop version of Outlook, highlight the email you want to send to the case and click the Send to Case button in the ribbon:
If you are using the Simplified Ribbon layout, you may need to click on the Apps icon in order to see the Send to Case add-in:
If you are using the new desktop Outlook, you will need to click on the Apps icon once an email is selected in order to see the Send to Case add-in:
The feature opens in a window on the right-hand side of the screen where you can log in to your Gardiant account and take the appropriate steps: