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.

Mailjet

Mailjet’s official plugin on WordPress gives you access to: 
– Easy Email Management: Create and manage all of your marketing and transactional email campaigns directly from your WordPress admin. 
– Sign Up Form & Contact Lists Management: Create and customize contact form widgets to allow your website visitors to subscribe to your newsletters. Add the subscription widget in any page or post using shortcode. 
– Automated Contact Synchronization – 4 ways to build your contact lists: 
 – Synchronize your WordPress users. The user role is added to Mailjet as a contact property, so you can filter and target marketing emails to the proper group. With ongoing synchronization, you never have to think about contact management again. 
 – Comment authors can be added to a separate Mailjet contact list as they choose to subscribe while posting a comment on the blog. 
 – Subscribe WooCommerce customers to your newsletter during checkout. Just enable the WooCommerce integration inside the plugin and you are ready to go. 
 – Use the built in Contact Form 7 integration and allow form submitters to subscribe to your newsletter. 
– Campaign Builder Tool: Use our drag and drop email editor or HTML builder to create beautiful and engaging emails – directly from your WordPress admin. 
– Flexibility – use filters to set your own subscription confirmation email template or texts inside the email, set your own thank you page, or widget form. See the FAQ for more details. 
– World Class Deliverability: Hit your subscribers’ inboxes every time with our global deliverability and routing infrastructure 
– Insight and analytics: Access real-time statistics on your campaigns showing opens, clicks, geographies, average time to click and more to optimize your email performance. 
– Data Compliance: Mailjet is GDPR compliant and ISO 27001 certified, meaning that it guarantees an optimal level of email data privacy and security. 
– International UI and Support: Mailjet offers user interfaces, documentation and 24/7 customer support in 5 languages (English, French, German, Spanish and Italian).
<h3>What’s new</h3>
<ul>
<li>Full WooCommerce support – use Mailjet’s drag and drop email builder to create responsive Order Notification and Abandoned cart reminder emails and engage with your customers at the right moment. Add newsletter subscribers from the “Check out” and the “Thank you” pages. Sync order data to Mailjet and use our powerful Segmentation and Automation features to target specific customer groups.</li>
<li>Shortcode support – add the subscription widget in any page or post using shortcode.</li>
<li>Integration with Contact Form 7 – add a “Subscribe to our newsletter” checkbox to any Contact Form 7 form and easily add subscribers to your contact lists</li>
</ul>

Mailjet Email Marketing


There are many problems with support (/support/plugin/mailjet-for-wordpress/), but there are no answers from the developer and unfortunately it still occurs and has not been resolved.



I'll probably update this star to a better one if anything changes


No support

Includes WooCommerce automated and order emails. Design, send and track engaging marketing and transactional emails from your WordPress admin.

Mailchimp List Subscribe Form vs Mailjet Email Marketing