thebluecube

This plugin adds some additional features to the Gravity Forms plugin:
<ul>
<li>Input ID change (if the form has not received any entries yet)</li>
<li>Advanced input validations</li>
<li>Form access control</li>
<li>Advanced conditional logic shortcode to be used in email notifications</li>
</ul>
Documentation: https://thebluecube.com/wordpress-plugins/bluecube-mighty-gravity-forms/documentation/

Blue Cube Mighty Gravity Forms

This plugin adds some additional features to the Gravity Forms plugin:

maranqz

The Cheapest advanced Email Address Validation to forms. Prevents typos in email address field and eliminates spam submissions with fake email addresses. The solution is based on Email Validator service.
Email validation is easy way to check and verify address by the validators: 
* Syntax; 
* Role; 
* Free domain; 
* Disposable 
* MX records; 
* SMTP (to check existing).
This plugin uses external service (Email Validator) and requires API Key which can be obtained <a href="https://rapidapi.com/maranqz/api/email-validator15/" rel="nofollow ugc">here</a>.
Please check Privacy Policy <a href="https://rapidapi.com/privacy/" rel="nofollow ugc">here</a> and Terms <a href="https://rapidapi.com/terms/" rel="nofollow ugc">here</a>.

GEV Email Validator

The Cheapest advanced Email Address Validation to forms. Prevents typos in email address field and eliminates spam submissions with fake email address …

Blue Cube Mighty Gravity Forms vs GEV Email Validator