shawfactor

mattsenate

This plugin is can be used for petitions, events, or any verified list and as far as I know is unique in WordPress.
Creating a petition/list/signup is as easy as adding a shortcode to a post or page (or CPT). From there additional editors are available to configure easch aspect of the sign up. Everything is completely self hosted and all list members become users of your site (not a third parties).
Available shortcodes:
[lh_signing_form] (enable signatories on any post, page, or custom post type)
Unconfirmed signatories: [lh_signing_unconfirmed_count]
Confirmed signatories: [lh_signing_confirmed_count]
Total signatories: [lh_signing_total_count]
[lh_signing_unconfirmed_list] (unformated list)
[lh_signing_confirmed_list] (unformated list)
You can customise the display of the signing form ([lh_signing_form]) via a number of shortcode arguments more information is available <a href="https://lhero.org/portfolio/lh-signing/" title="Additional Plugin documentation" rel="nofollow ugc">here</a>

LH Signing

LH Signing allows you to create configurable validated lists like petitions or event sign ups. It is the only self hosted solution in WP

quickemailverification

An email verification plugin by <a href="http://quickemailverification.com" rel="nofollow ugc">QuickEmailVerification</a> enables you to validate and verify the email address existence in real time, before you actually send them an email. Its unique email verification system is composed of multiple different validations starting from syntax checking to the end users’ mailbox existence checking. It not only detects invalid email addresses but also detects many other types of poor email addresses which could negatively impact the email deliverability and harm your sender reputation.
This plugin need a QuickEmailVerification API key to verify. You can get it from <a href="https://quickemailverification.com/apisettings" title="Get your API key" rel="nofollow ugc">API settings</a> page of QuickEmailVerification service.
<h4>Key features</h4>
<ul>
<li>Email address syntax checking</li>
<li>Domain/MX records checking</li>
<li>Role address detection</li>
<li>Disposable email address (DEA) detection</li>
<li>Free email service detection</li>
<li>Typo detection and suggestion</li>
<li>Accept all email checking</li>
<li>Mailbox existence checking</li>
</ul>
<h4>Supported form Plugins</h4>
<ul>
<li>Contact Form 7</li>
<li>Formidable forms</li>
<li>Ninja forms</li>
<li>WooCommerce</li>
<li>WPForms</li>
<li>Profile Builder</li>
<li>Contact Form by BestWebSoft</li>
<li>Ultimate Member registration form</li>
<li>Fluent Forms</li>
<li>WPEverest forms</li>
<li>MailPoet</li>
<li>Theme My Login</li>
<li>WP-Members</li>
<li>Visual Form Builder</li>
<li>PlanSo forms</li>
<li>Buddypress registration form</li>
<li>Any other form which uses the is_email() function</li>
</ul>
This plugin works either with “is_email()” function or with any other supported form plugins. So if any supported form plugin is enabled, “is_email()” hook will automatically be disabled.
To know more about email verification results, please have a look at the <a href="http://docs.quickemailverification.com/getting-started/understanding-email-verification-result" rel="nofollow ugc">QuickEmailVerification knowledge base</a>.

QuickEmailVerification

The QuickEmailVerification email verification plugin to avoid fake, bad and nonexistent emails.

LH Signing vs QuickEmailVerification