- If you have an action to complete in a mail that was sent to you, you have the option to add more reviewers to the mail.
 - The reviewers that you add will also get an action that they need to complete.
 - To add reviewers to a mail, open the mail and click on the '+Add' button under the Reviewers tab.
 

- In the dialog that opens, select the reviewers.
 - They will be added to the mail, and actions will be generated for them to complete.