Formidable Forms is a very complete WordPress form builder that connects with Jackmail.
Jackmail is a WordPress plugin that allows you to create and send email marketing campaigns directly from your WordPress dashboard.

This integration allows Jackmail to synchronize emails collected from Formidable Forms’ forms. You’ll be able to pick and use the emails in your campaigns.
If you have not activated the Formidable Forms extension when you first installed Jackmail, then go to the “Settings” of your jackmail account and seclect the “Formidable Forms” extension by ticking the corresponding box in the “Integrated extensions” section.

There’s nothing else to do since Jackmail will simply synchronize with the lists created in Formidable Forms.
In the “Lists” section, you will now find the synchronized lists provided by the plugins you have implemented (in our case Formidable Forms but there can be other synchronized lists comings from different activated plugins).

Please note: Your lists have been created with Formidable Forms, therefore you’ll have to edit/delete entries directly in this extension, and not in Jackmail.