When it comes to collecting email addresses, marketers can choose between single or double opt-in validation. Single opt-in tends to generate more bounces, blacklisting or spam trap hits, hurting your deliverability rates. This is why it’s recommended to use double opt-in. Double opt-in adds an additional step to the subscription opt-in process by asking users to click on an email link sent to them after their registration to confirm their subscription.

A double opt-in process is recommended to eliminate mis-typed or fake email addresses, but also to make sure your recipients are really interested in receiving your emails. This will allow you to have better engagement rates and fewer unsubscribes and emails marked as spam, and ultimately help you ensure a good email deliverability. Also, even if it’s not mandatory, using a double opt-in process is a great way to ensure compliance regarding consent under the General Data Protection Regulation (GDPR).
To collect email addresses via a double opt-in process, make sure to use an Email Service Provider (ESP) that offers double opt-in subscription widgets (a piece of code that you can add to your site, which renders basic form), and set them up on your website:
Result
Double opt-in for email subscription is known to be one of the most effective ways to improve your reader engagement and the deliverability of your email marketing campaigns.