Mailchimp

Use the Mailchimp List Subscribe plugin to quickly add a Mailchimp signup form block, widget, or shortcode to your WordPress site.
After installation, if you already have a Mailchimp account, you’ll log in with that account and then proceed to configure settings.
If you don’t have an account, you can create one directly in the plugin. After entering in all your personal details, you’ll need to activate your account via an email that will be sent to you. Once done, you’ll proceed to configure settings.
On the settings screen, you’ll select your Mailchimp list, choose merge fields and groups, and configure other options. Once done, you can now add the block, widget, or shortcode (<code>[mailchimpsf_form]</code>) to your site. Typically, installation and setup will take about 5-10 minutes, and absolutely everything can be done via the WordPress Setting GUI, with no file editing at all.
WordPress.com compatibility is limited to Business tier users only. <a href="https://mailchimp.com/help/ways-to-add-a-signup-form-in-wordpress/" rel="nofollow ugc">How to add a signup form if you have a WordPress.com site</a>.
<h3>Access Token Encryption</h3>
Starting in version 1.6.0, authentication has changed to use OAuth. As part of this process, we retrieve an access token that can be used to make API requests. To provide a high-level of security, this access token is encrypted before being stored in the WordPress database. In order to ensure this access token can be decrypted when used, the plugin relies on certain security constants that should remain unchanged.
With no additional configuration, we use the standard <code>LOGGED_IN_KEY</code> and <code>LOGGED_IN_SALT</code> constants that are normally set in your site’s <code>wp-config.php</code> file. Some sites make use of security plugins that rotate these constants on a periodic basis. When this happens, we won’t be able to decrypt the access token and you’ll need to reconnect your Mailchimp account to generate a new access token.
To prevent such issues, it is recommended to define two additional constants in your site’s <code>wp-config.php</code> file: <code>MAILCHIMP_SF_ENCRYPTION_KEY</code> and <code>MAILCHIMP_SF_ENCRYPTION_SALT</code>. These constants should consist of a combination of characters, preferably at least 32 characters long. Once set, these values should not be changed. For strong values, you can copy some of the values from <a href="https://api.wordpress.org/secret-key/1.1/salt/" rel="nofollow ugc">here</a> and use them. You’ll end up with additional code like the following in your <code>wp-config.php</code> file:
<pre><code>define( 'MAILCHIMP_SF_ENCRYPTION_KEY', 'put your unique phrase here' );
define( 'MAILCHIMP_SF_ENCRYPTION_SALT', 'put your unique phrase here' );
</code></pre>
If these constants are added after you’ve already authenticated with Mailchimp, you will need to reconnect your account. To avoid this, you can copy the values from <code>LOGGED_IN_KEY</code> and <code>LOGGED_IN_SALT</code> (if they exist) to <code>MAILCHIMP_SF_ENCRYPTION_KEY</code> and <code>MAILCHIMP_SF_ENCRYPTION_SALT</code> respectively.
<h3>Upgrading</h3>
If you are upgrading to version 1.2.1 and you used the widget in your sidebar previously, all you need to do is drag the <code>Mailchimp Widget</code> back into the sidebar, visit the Mailchimp settings page (which will have maintained your prior settings), click the “Update List” button, and you’re done!

Mailchimp List Subscribe Form

Add a Mailchimp signup form block, widget, or shortcode to your WordPress site.

jaromy

<h4>Sign Me Up</h4>
This plugin is a widget that adds a simple sign-up form to your WordPress site, allowing visitors to subscribe to your mailing list. It serves as a front end to <a href="http://www.phplist.com" rel="nofollow ugc">phpList</a>, the most popular open-source newsletter manager (over 1.5 million downloads according to their website). The widget connects to phpList via AJAX, which allows a visitor to subscribe without leaving your WordPress page – no refresh or redirect is necessary.
Features:
<ul>
<li>Add a simple “sign-up to our newsletter” form to your WordPress site</li>
<li>Provides a back-end connection to the powerful open-source mailing list manager, phpList </li>
<li>Maintains the consistent look, feel, and branding of your WordPress site</li>
<li>Uses AJAX – no page refresh or redirects. Status & feedback are displayed on the same page as the form</li>
<li>Minimal, elegant, simple. Seamlessly blends in with your theme by incorporating existing styling rules</li>
<li>Easy customization – change the text of each form element so it says exactly what you want</li>
<li>Widgetized – easily add it to your site via drag & drop</li>
<li>Error checking – client side validation via popular jQuery Validation library provides immediate feedback to the user and reduces erroneous data</li>
</ul>
More information
<ul>
<li><a href="http://www.jaromy.net/wordpress-plugins/sign-me-up/" rel="nofollow ugc">Sign Me Up</a></li>
</ul>

Sign Me Up

Add a simple straightforward sign-up form to your WordPress site. Integrates with phpList, the most popular open-source newsletter manager.

Mailchimp List Subscribe Form vs Sign Me Up