Aaron D. Campbell

This plugins gives you a great framework to use for integrating with MailChimp.
Requires PHP5.

MailChimp Framework

MailChimp integration framework and admin interface as well as WebHook listener.  Requires PHP5.

arisoft

Easy to use integration of Contact Form 7 with MailChimp, MailerLite and Zapier services. List of the supported services are constantly grow.
Helps to extend your subscription lists and collect unlimited leads. Transform forms to powerful marketing tool.
<h4>Features</h4>
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Simple and easy to use interface. Just specify an API key and the plugin shows all available lists / fields. No need to find and remember any group / list / field ID.
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Can update existing subscribers and supports double opt-in mode to send a confirmation mail for MailChimp
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Populate Mailer Lite and Mail Chimp custom fields with values of form elements
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Cache data from 3rd party services to increase performance
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We are always open for new ideas and offer reactive support
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</ul>
<blockquote>
<h4>Need more features?</h4>
Upgrade to <a href="http://contact-form-7-connector.ari-soft.com/#pricing" rel="nofollow ugc">PRO version</a> with the following features:
</blockquote>
<ul>
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Connect CF7 with Zapier service. Zapier provide integration with 500+ popular services: ActiveCampaign, AWeber, ConstantContact, Drip, InfusionSoft, GetResponse and etc.
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Supports segmentation for MailChimp
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Register unlimited number of shared API key for MailerLite / MailChimp
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Subscribe to different lists / groups depends on the selected form value
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</ul>
<h4>System requirements</h4>
The plugin works with WordPress 4.0+, PHP 7.1+ and “Contact Form 7” 4.2+
More information can be found in <a href="http://www.ari-soft.com/docs/wordpress/contact-form-7-connector/v1/en/index.html" rel="nofollow ugc">user’s guide</a>.
Have any question, a support request or ideas how to do the plugin better?
Contact us <a href="http://www.ari-soft.com/Contact-Form-7-Connector/" rel="nofollow ugc">here</a> and we will contact and help you shortly.
Like the plugin?
We would be grateful for a review <a href="https://wordpress.org/support/plugin/ari-cf7-connector/reviews/" rel="ugc">here</a>.
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Contact Form 7 Connector

I was using another contact form 7 extension to integrate with Mailchimp, but it was hard to make it work, this plugin worked like a charm!

Perfect!

MailChimp, MailerLite and Zapier integration with Contact Form 7. Use form data smartly. Generate unlimited leads and extend mailing lists.

MailChimp Framework vs Contact Form 7 Connector