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

ilGhera

If you’re using MailUp as newsletter service, you can add your users to it in the same time they’re registering to your site. 
You’ll be able to set the MailUp List ID, Group ID and much more.

MailUp Auto Subscription

Let users subscribe to MailUp newsletter service in the same time they're registering to your site.

Popup Maker Addon for Newsletter vs MailUp Auto Subscription