We'll create fresh WordPress site with Add-on Gravity Forms – MailPoet 3 installed. You have 20 minutes to test the plugin after that site we'll be deleted.
Requirements
Create MailPoet Newsletter subscribers from Gravity Forms entries.
Requires Gravity Forms version 1.9.16 or higher and MailPoet 3.0 or higher.
MailPoet is a free newsletter and post notification plugin for WordPress that makes it really simple to send out email newsletters to your subscription lists. This plugin integrates Gravity Forms with MailPoet by providing an option for your customers to signup for your newsletter lists while submitting a form.
First edit any Mailpoet form and add a custom field
http://prntscr.com/ntrzbt
Now create/edit a gravity form and add an exact field
http://prntscr.com/nts0cw
Now hover on the “MailPoet custom field ID” tooltip and copy the ID. Paste that ID to the “MailPoet custom field ID” field
http://prntscr.com/nts26o
That’s it. Now gravity form field will be synchronized with MailPoet’s subscriber field.