Stefano Lissa

This simple and little plugin integrates the <a href="https://wordpress.org/plugins/popup-maker/" rel="ugc">Popup Maker</a> plugin with forms 
of <a href="https://wordpress.org/plugins/newsletter/" rel="ugc">Newsletter</a> plugin, usually generated via 
shortcodes. It follows the Popup Maker standard integration methods.
Note: this plugin should be considered as developed indipendently from Newsletter and Popup Maker. For support, contribution and so on 
use the support area provided by wordpress.org. Much appreciated.
<h4>Other Newsletter plugin integrations</h4>
<ul>
<li><a href="https://wordpress.org/plugins/newsletter-buddypress" rel="ugc">BuddyPress</a></li>
</ul>

Popup Maker Addon for Newsletter

Adds support to Popup Maker for Newsletter subscription forms

vinzzb

This plugin imports forms from you PhpList host into wordpress. 
Your subscription forms can be used anywhere in wordpress using shortcodes. 
Custom user attributes defined in phplist are also taken into account. 
The plugin uses async calls (ajax) for registrations. You can fully customize the respone on success or failures.
NOTE: This plugin will only work with self hosted PhpList environments. It does not work with phplist.com accounts.
<a href="http://coderisk.com/wp/plugin/phpls/RIPS-6cAWMzmXxg" rel="nofollow ugc"></a>

PhpList Subber

Integrate your PhpList subscription forms in Wordpress, including user attributes in phpList.

Popup Maker Addon for Newsletter vs PhpList Subber