Whitelist URLs outside the Salesforce domain that your users can navigate to directly when the Warn users before they are redirected outside of Salesforce setting is enabled. For URLs that you don’t whitelist, users see a warning message before they get redirected.
Where: This change applies to Salesforce Classic in all editions.
How: From Setup, in the Quick Find box, enter Whitelisted URLs for Redirects, and then select Whitelisted URLs for Redirects. Click New URL