1. Create a subscriber list.
2. Click the Double Opt-In tab.
3. Click the Require subscribers to provide confirmation of valid email address checkbox.
4. Click Select.
5. Choose the email which contains the double opt-in substitution string %%double_opt_in_url%%.
6. Select Opt-In Landing Page.
7. Enter the email address used to receive the blank email double opt-in messages. The reply mail management configuration automatically adds the domain for the email address, and you cannot change this portion of the email address.
8. Optionally, you can select a Salesforce Marketing Cloud or external opt-in landing page to display to subscribers when that subscriber clicks the double opt-in link URL.