Zack Katz

Add a StreamSend Signup Form to Your Website
Easily add a StreamSend Sign-up Form to your website with this plugin. When users sign up for your StreamSend newsletter, they will be signing up on your website, not on the StreamSend website.
Works well with the <a href="https://wordpress.org/extend/plugins/show-content-only/" rel="ugc">Show Content Only plugin</a>. Used together, you can create a page that is only the signup form, but still running on WordPress.
Note: this plugin requires an active <a href="http://www.streamsend.com/" rel="nofollow ugc">StreamSend account</a>.

StreamSend WordPress Plugin

Add a StreamSend Signup Form to Your Website

ezpublishing

Quickly and easily add highly customizable sign-up forms to your WordPress website. Simply install the plugin and the setup page will guide you through the rest. All you need is your StreamSned API login information to create your forms.
<ul>
<li>Create unlimited number of forms, each subscribing to one or multiple StreamSend lists</li>
<li>Easily create and style your form, no coding required</li>
<li>Add a signup form to your WordPress sidebar using a widget or shortcode</li>
<li>Add an opt-in message to your form</li>
<li>Determine which lists should appear as “opt-in lists” on the form and which lists should remain be hidden</li>
<li>Create and send welcome messages to members who join via your WordPress signup form</li>
</ul>

StreamSend for WordPress – Official Plugin

Quickly and easily add highly customizable sign-up forms to your WordPress website.

StreamSend WordPress Plugin vs StreamSend for WordPress – Official Plugin