> For clean Markdown of any page, append .md to the page URL.
> For a complete documentation index, see https://mailchimp.com/developer/release-notes/llms.txt.
> For AI client integration (Claude Code, Cursor, etc.), connect to the MCP server at https://mailchimp.com/developer/_mcp/server.

# Release Notes

> Find all the Mailchimp API documentation and tools developers need to send marketing and transactional emails.

## Docs

- [Mailchimp Transactional status added to server status page](https://mailchimp.com/developer/release-notes/2025/8/19.md)
- [New Audiences endpoints (BETA)](https://mailchimp.com/developer/release-notes/2025/8/7.md)
- [Overwriting campaign_id and outreach_id](https://mailchimp.com/developer/release-notes/2024/12/6.md)
- [Webhook retry interval increased](https://mailchimp.com/developer/release-notes/2024/6/17.md)
- [Updated Mailchimp Transactional client libraries](https://mailchimp.com/developer/release-notes/2024/2/12.md)
- [New sending domain authentication requirements](https://mailchimp.com/developer/release-notes/2023/12/19.md)
- [Changing API server response for client errors](https://mailchimp.com/developer/release-notes/2023/7/3.md)
- [Response code updated for invalid template name](https://mailchimp.com/developer/release-notes/2023/6/17.md)
- [Retiring legacy versions of Transport Layer Security (TLS) protocol](https://mailchimp.com/developer/release-notes/2023/6/5.md)
- [Export API 1.0 and API 2.0 no longer supported](https://mailchimp.com/developer/release-notes/2023/6/1.md)
- [Added client secret rotation functionality](https://mailchimp.com/developer/release-notes/2023/4/20.md)
- [Subject and TO header no longer require encoding](https://mailchimp.com/developer/release-notes/2023/4/19.md)
- [Changing messages/info server response](https://mailchimp.com/developer/release-notes/2023/4/14.md)
- [Message search rate limit now enforced](https://mailchimp.com/developer/release-notes/2023/4/10.md)
- [Added support for 401 Unauthorized response code](https://mailchimp.com/developer/release-notes/2023/2/23.md)
- [Updated export download security](https://mailchimp.com/developer/release-notes/2023/2/21.md)
- [Added empty alt tag to tracking pixels](https://mailchimp.com/developer/release-notes/2023/1/12.md)
- [Added a field to various Transactional responses when messages are queued](https://mailchimp.com/developer/release-notes/2022/11/8.md)
- [Added time limit to message scheduling](https://mailchimp.com/developer/release-notes/2022/10/6.md)
- [IP validation now enforced on Add or Update List Member](https://mailchimp.com/developer/release-notes/2022/9/1.md)
- [Additional fields added to Batch Subscribe error response](https://mailchimp.com/developer/release-notes/2022/8/3.md)
- [Added transactional as an accepted status for Batch Subscribe](https://mailchimp.com/developer/release-notes/2022/8/2.md)
- [Error displayed for Transactional Demo users who are over their inbound quota](https://mailchimp.com/developer/release-notes/2022/5/17.md)
- [Added Survey Reporting](https://mailchimp.com/developer/release-notes/2022/4/25.md)
- [Added new webhook event type](https://mailchimp.com/developer/release-notes/2022/3/1.md)
- [Added ability to sync tags to existing members](https://mailchimp.com/developer/release-notes/2022/1/24.md)
- [Batch API limit now considers pending batch webhooks](https://mailchimp.com/developer/release-notes/2021/11/16.md)
- [Added camelCase support to Handlebars](https://mailchimp.com/developer/release-notes/2021/10/29.md)
- [Fixed Rejection Denylist display](https://mailchimp.com/developer/release-notes/2021/10/4.md)
- [Added new Allowlists series of endpoints](https://mailchimp.com/developer/release-notes/2021/9/23.md)
- [Cleaning up batch webhooks when deleting API keys or app connections](https://mailchimp.com/developer/release-notes/2021/9/22.md)
- [Data changes with Apple Mail Privacy Protection](https://mailchimp.com/developer/release-notes/2021/9/14.md)
- [Adding a limit to Batch Webhooks](https://mailchimp.com/developer/release-notes/2021/9/7.md)
- [Removing Campaign tracking tags](https://mailchimp.com/developer/release-notes/2021/8/25.md)
- [Domain verification via TXT record](https://mailchimp.com/developer/release-notes/2021/8/24.md)
- [Mailchimp Stores read-only in API](https://mailchimp.com/developer/release-notes/2021/8/19.md)
- [Added ability to delete multiple tags](https://mailchimp.com/developer/release-notes/2021/8/12.md)
- [Full timestamp for bounces](https://mailchimp.com/developer/release-notes/2021/7/27.md)
- [Open Details reporting now handles query parameters correctly](https://mailchimp.com/developer/release-notes/2021/7/22.md)
- [Descriptive errors when adding E-commerce customers](https://mailchimp.com/developer/release-notes/2021/7/19.md)
- [List carts returns the created and updated date](https://mailchimp.com/developer/release-notes/2021/7/14.md)
- [Fixed Get Campaign Info to return total clicks for parent automations and variates](https://mailchimp.com/developer/release-notes/2021/7/12.md)
- [Changes to List visibility](https://mailchimp.com/developer/release-notes/2021/6/3.md)
- [Better JSON parsing errors](https://mailchimp.com/developer/release-notes/2021/5/19.md)
- [Full name added to member responses](https://mailchimp.com/developer/release-notes/2021/5/18.md)
- [Stability improvements to API batch jobs](https://mailchimp.com/developer/release-notes/2021/5/10.md)
- [Planned router maintenance](https://mailchimp.com/developer/release-notes/2021/4/20.md)
- [Returning a 410 from an audience webhook will disable it](https://mailchimp.com/developer/release-notes/2021/4/5.md)
- [Fixing a PHP client library include and exclude fields bug](https://mailchimp.com/developer/release-notes/2021/3/17.md)
- [Better error on invalid request to ecommerce/stores/.../orders](https://mailchimp.com/developer/release-notes/2021/3/15.md)
- [Handling boolean query parameters](https://mailchimp.com/developer/release-notes/2021/3/2.md)
- [Addition of Customer Journey API trigger endpoint](https://mailchimp.com/developer/release-notes/2021/2/25.md)
- [Transactional search infrastructure improvements](https://mailchimp.com/developer/release-notes/2021/2/22.md)
- [Mobile SDK for iOS adds Swift Package Support](https://mailchimp.com/developer/release-notes/2021/2/18.md)
- [Changes when using multiple authorization methods](https://mailchimp.com/developer/release-notes/2021/2/17.md)
- [Deprecating the Link Application endpoint](https://mailchimp.com/developer/release-notes/2021/1/26.md)
- [Require PHP 7 in Marketing and Transactional SDKs](https://mailchimp.com/developer/release-notes/2021/1/25.md)
- [Updated Swagger and API reference to match endpoint requirements](https://mailchimp.com/developer/release-notes/2020/12/23.md)
- [Improved HTTP status for unhandled methods](https://mailchimp.com/developer/release-notes/2020/12/16.md)
- [Performance improvement for Email Activity Reports](https://mailchimp.com/developer/release-notes/2020/12/11.md)
- [Fixed behavior for customers added via E-commerce endpoints](https://mailchimp.com/developer/release-notes/2020/12/7.md)
- [Incorrectly returning messages for all conversations](https://mailchimp.com/developer/release-notes/2020/12/3.md)
- [Improved performance of List Member Activity](https://mailchimp.com/developer/release-notes/2020/12/1.md)
- [Fixing the query parameter documentation for List Templates](https://mailchimp.com/developer/release-notes/2020/11/25.md)
- [Improving the _links](https://mailchimp.com/developer/release-notes/2020/11/24.md)
- [Transactional database infrastructure improvements](https://mailchimp.com/developer/release-notes/2020/11/19.md)
- [Better handling of rss_opts for POST Campaigns](https://mailchimp.com/developer/release-notes/2020/11/9.md)
- [Updated list automations query parameters](https://mailchimp.com/developer/release-notes/2020/11/4.md)
- [Deprecating the Update Automation endpoint](https://mailchimp.com/developer/release-notes/2020/11/2.md)
- [Internal infrastructure improvements](https://mailchimp.com/developer/release-notes/2020/10/19.md)
- [Assorted spec and documentation fixes](https://mailchimp.com/developer/release-notes/2020/10/13.md)
- [Ensuring codegen references latest Swagger spec](https://mailchimp.com/developer/release-notes/2020/10/1.md)
- [Deprecated fields in the Growth History endpoint](https://mailchimp.com/developer/release-notes/2020/8/27.md)
- [New client libraries for Marketing and Transactional APIs](https://mailchimp.com/developer/release-notes/2020/8/24.md)
- [Preventing multiple confirmation emails on PATCH or PUT to Lists/Member endpoint](https://mailchimp.com/developer/release-notes/2020/8/19.md)
- [Stricter rules for URL matching in OAuth 2](https://mailchimp.com/developer/release-notes/2020/8/11.md)
- [Obfuscated emails on the Unsubscribe page](https://mailchimp.com/developer/release-notes/2020/5/4.md)
- [Improved error messaging on malformed requests to the Members endpoint](https://mailchimp.com/developer/release-notes/2020/4/18.md)
- [API Swagger spec now OAS 2-compliant](https://mailchimp.com/developer/release-notes/2020/3/13.md)
- [Minor improvement to parameter handling in the Events endpoint](https://mailchimp.com/developer/release-notes/2020/2/26.md)