Configure the Subscribe Form module for MailChimp double opt-in

MailChimp changed their default subscriber setting to single opt-in – in other words, a subscriber submits a subscription form connected to the MailChimp API and is automatically subscribed. Double opt-in is when the subscriber submits the form and receives an email asking for subscription verification.

If you're using the Beaver Builder Subscribe Form module, you can enable double opt-in with a Beaver Builder filter. See the filter examples article for the MailChimp opt-in filter code.