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.

GetResponse

<h4>GetResponse for WordPress</h4>
GetResponse for WordPress lets you add site visitors to your contact list, update contact information, and add your GetResponse landing pages to your WordPress site as a page. Use it to track site visits and pass ecommerce data to GetResponse. The plugin helps grow your contact list and ensures you have the contact information and ecommerce data to plan successful marketing campaigns.
The plugin features include:
<h3>List-building options</h3>
Encourage people to sign up using all the list-building options and built-in integrations with Contact Form 7, BuddyPress and Ninja Forms:
<ul>
<li>add GetResponse forms anywhere on your site and to your blog posts,</li>
<li>add an opt-in box to comments and registration forms to add site visitors to your list,</li>
<li>add an opt-in box to Contact Form 7, Ninja Forms and BuddyPress forms.</li>
</ul>
Add GetResponse landing pages on your WordPress site to:
<ul>
<li>easily feature new webinar, signup, promotion, download, or sales-focused pages,</li>
<li>use popup, exit popup, and fixed bar forms on the pages to get more signups,</li>
<li>run A/B tests to ensure your page design is optimized for conversions,</li>
<li>easily publish landing pages under your WordPress domain as a subpage,</li>
<li>add contacts without any 3rd party integrations directly after they sign up from one of your landing pages.</li>
</ul>
<h3>WooCommerce – add contacts and collect ecommerce data</h3>
The built-in integration with WooCommerce lets you add customers to your contact list and send ecommerce data to GetResponse. Here’s what you can do with it:
<ul>
<li>grow your list by adding customers at checkout,</li>
<li>export customer list to GetResponse (this option allows you to export custom fields and purchase history),</li>
<li>collect information about customer spending habits, products, purchases made, and shopping carts.</li>
</ul>
<h3>Web Event tracking</h3>
GetResponse for WordPress lets you track visits to your site. Create workflows based on URLs visited. Use advanced search options to identify people who recently visited your site. You can create custom filters and plan your mailings.
Have questions? Head to our <a href="https://www.getresponse.com/help/integrations-and-api#subcat-wordpress-integration" rel="nofollow ugc">Help Center</a> for more information about installing the features in the plugin.

GetResponse for WordPress

Take advantage of your visitors' commentators' and customers' interest. Invite them to subscribe and nurture their engagement.

Mailchimp List Subscribe Form vs GetResponse for WordPress