Title: Mailchimp error
Last modified: July 1, 2026

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# Mailchimp error

 *  Resolved [pixelshrink](https://wordpress.org/support/users/pixelshrink/)
 * (@pixelshrink)
 * [5 days, 10 hours ago](https://wordpress.org/support/topic/mailchimp-error-9/)
 * Hi, ever since a website has been migrated, the signup form via Ninja Forms hasn’t
   worked. The error in the logs is:
 * 2026-07-01 12:01:50: 400: The resource submitted could not be validated. For 
   field-specific details, see the ‘errors’ array. – ({“type”:”[https://mailchimp.com/developer/marketing/docs/errors/&#8221](https://mailchimp.com/developer/marketing/docs/errors/&#8221);,”
   title”:”Invalid Resource”,”status”:400,”detail”:”The resource submitted could
   not be validated. For field-specific details, see the ‘errors’ array.”,”instance”:”…”,”
   errors”:[{“field”:”ip_signup”,”message”:”This value is not a valid IP. Valid 
   IPs have a format of W.X.Y.Z where each letter represents a number between 0-
   255.”}]})
 * Please can you advise how to fix this?

Viewing 3 replies - 1 through 3 (of 3 total)

 *  Plugin Support [Ibrahim Nasir](https://wordpress.org/support/users/ibrahimkh4l33l/)
 * (@ibrahimkh4l33l)
 * [5 days, 9 hours ago](https://wordpress.org/support/topic/mailchimp-error-9/#post-18953141)
 * Hello [@pixelshrink](https://wordpress.org/support/users/pixelshrink/) 👋🏽,
 * This issue is usually caused by browsers’ inability to access the user’s IP address(
   mainly on Safari or MacOs), which Mailchimp requires for spam protection. You
   can ask the user to try another browser/device or you can skip sending the IP
   data to Mailchimp.
 * If you want to skip sending the IP data to Mailchimp, please add the code snippet
   below to your active theme’s function.php file or via the [Code Snippets plugin.](https://wordpress.org/plugins/code-snippets/)
 *     ```wp-block-code
       /** Stop sending subscribers IP address during mailchimp optin subscription */add_filter('mo_connections_mailchimp_subscription_parameters', function ($parameters) {  unset($parameters['ip_signup']);                return $parameters;});
       ```
   
 * Please note that Mailchimp uses IP addresses to detect bot submissions. If a 
   user’s browser can’t read their IP address, the submission fails the bot test,
   and the error is logged. If you skip sending the IP data to Mailchimp, you might
   see an increase in spam.
 * Cheers
 *  Thread Starter [pixelshrink](https://wordpress.org/support/users/pixelshrink/)
 * (@pixelshrink)
 * [5 days, 7 hours ago](https://wordpress.org/support/topic/mailchimp-error-9/#post-18953244)
 * Great, thanks. It’s a website that’s being run through Cloudflare so would it
   be that that is the problem with the IP address? If so is there a workaround 
   or will we still need to switch off IP address submissions? This happened on 
   Windows so it’s not a Mac issue.
 *  Plugin Support [Ibrahim Nasir](https://wordpress.org/support/users/ibrahimkh4l33l/)
 * (@ibrahimkh4l33l)
 * [5 days, 6 hours ago](https://wordpress.org/support/topic/mailchimp-error-9/#post-18953346)
 * Yes, Cloudflare is very likely the cause here. Mailchimp’s `ip_signup` field 
   only accepts **IPv4** addresses, and Cloudflare serves and forwards traffic over
   IPv6 by default, so the IPv6 address sent to Mailchimp is rejected, causing this
   issue.
 * The filter I shared above will fix this for now. We’ve also updated the integration
   so that, in our next release, MailOptin will no longer send IPv6 addresses to
   Mailchimp’s `ip_signup` field.
 * I’ll let you know once that update is available so you can remove the filter 
   and benefit from Mailchimp’s spam protection for IPv4 users.
 * Best regards

Viewing 3 replies - 1 through 3 (of 3 total)

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 * ![](https://ps.w.org/mailoptin/assets/icon-256x256.png?rev=1699978)
 * [MailOptin - Popup, Optin Forms & Email Newsletters for Mailchimp, HubSpot, AWeber Etc.](https://wordpress.org/plugins/mailoptin/)
 * [Frequently Asked Questions](https://wordpress.org/plugins/mailoptin/#faq)
 * [Support Threads](https://wordpress.org/support/plugin/mailoptin/)
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 * 4 replies
 * 2 participants
 * Last reply from: [Ibrahim Nasir](https://wordpress.org/support/users/ibrahimkh4l33l/)
 * Last activity: [5 days, 6 hours ago](https://wordpress.org/support/topic/mailchimp-error-9/#post-18953346)
 * Status: resolved