When you activate the double opt-in option this means that any reader who subscribes to your publication must confirm the request twice. 

The reader enters the email address in the subscribe form and clicks the button to subscribe. This is the first opt-in. 

After this, a confirmation email is sent to the email address provided before. This email contains a link which the reader must click to confirm the subscription request. This is the second opt-in. 

Why do you need to activate the double opt-in option?

Though you don't miss out the leads that do not confirm their email address by using a single opt-in, you likely get a lot of fake or spam emails.

Using a double opt-in you get better engagement of your leads. 

Non-existing email addresses or the ones with typos will not be added to your list of subscribers automatically.

This way you guarantee that only the leads who are really interested will be converted into subscribers.  

How to activate the double opt-in:

For activating this option, follow the steps below: 

When activating free subscription for your publication check the Send a double opt-in confirmation email box. 

That's it! After filling in the subscribe form, your readers will see the following message.