Step 1: Login to the Plesk panel with your admin login credentials.
Step 2: Click the Website and Domain section and select the domain for that you are going to set the DKIM authentication.
Step 3: Then select the Mail setting option under the Mail tab.
Step 4: Enable the ‘Use DKIM spam protection system to sign outgoing email messages’ check box.
Step 5: Click How to Configure External DNS, then copy the DKIM records that are shown.
Step 6: Click OK to save the changes that are made.
Step 7: The copied DKIM records should be added to the DNS Template option under the Tools and Settings section.