Mailchimp for TYPO3

The mailchimp extension brings signups, interest groups included, straight into Mailchimp lists

Like koning_mailchimp_signup, the mailchimp extension is a signup form: visitors subscribe to a specific Mailchimp list on the website. It goes further than the older extension, which ends at TYPO3 8, though: editors choose the list and, if needed, an interest group in the content element, the form is a freely customizable Fluid template, and since version 3.0.0 a single TYPO3 installation can serve several Mailchimp accounts. The extension does not reconcile entire lists, show campaign figures in the backend or build newsletter templates from TYPO3 content; every signup goes straight to the Mailchimp API, with no sync jobs involved.

The GDPR remains central all the same: every signup sends the email address, first and last name, the selected interest groups and, optionally, up to ten further fields to Mailchimp. Without a data processing agreement with Mailchimp and a documented mechanism for the US transfer, this is not permissible under data protection law. (UK: Transfers from the UK to the US rely on the UK-US data bridge, the UK extension to the Data Privacy Framework.)

Typical use cases are newsletter signup, topic selection and multiple brands

The main scenario is newsletter signup on the website. Visitors enter their email address and name, the extension adds them to the selected list with the status “pending”, and Mailchimp sends the confirmation email for the double opt-in. The address only becomes active once the confirmation link is clicked. Mailchimp manages the list, unsubscribes and bounces; the extension creates no tables of its own in TYPO3.

The second scenario is topic selection through interest groups. If you offer several newsletters or topics, you create an interest group in Mailchimp, and the form shows the topics as checkboxes, radio buttons or a drop-down list, depending on the type of group. The signup lands in the list together with the selected topics, so marketing can send to individual groups in Mailchimp in a targeted way.

The third scenario is several brands or countries in one TYPO3 installation. Since version 3.0.0, you can store several labeled API keys, and editors choose in the content element which Mailchimp account and which list a form sends to. In the page module, the extension shows the account, list, interest group and current number of subscribers for each form. Open and click rates, on the other hand, are only visible to people with access to the Mailchimp dashboard.

The technical architecture calls Mailchimp API v3 directly on submit

The extension communicates through the Mailchimp Marketing API v3, which it addresses via a bundled PHP library. Authentication uses an API key stored in the TYPO3 Extension Manager. There is no scheduler task: every signup goes straight to Mailchimp when the form is submitted.

On submit, the extension adds the member to the selected list, with the status “pending” if double opt-in is used, otherwise directly as “subscribed”. If the address is already in the list but not subscribed, the extension updates the entry; the member ID is the MD5 hash of the email address. If the address is already subscribed, the form shows a notice.

The form is a Fluid template that can be overridden in your own site package. With the typoscript_rendering extension, it submits via Ajax without reloading the page. An email address can be prefilled via a GET or POST parameter, for example when another form points to the signup.

Developers connect further fields through a hook: the form supports up to ten additional fields, and the hook defines how they map to the fields in Mailchimp. The extension has no backend module of its own and no campaign metrics.

Common problems are required fields, existing addresses and disabled double opt-in

Problem one: required fields. If fields are marked as required in Mailchimp, the extension cannot check them on the server side, according to its documentation; if such a field is missing, the form only reports a generic error. The fix: mark the same fields as required in the Fluid template and validate them before submission.

Problem two: addresses that are already on the list. If an address is already subscribed, Mailchimp rejects the second signup, and the form reports that the address is already registered. Addresses that unsubscribed earlier, on the other hand, are signed up again by the extension. The fix: word the message clearly in the language file so that nobody thinks the signup failed.

Problem three: switching off double opt-in. By default, the extension asks for confirmation by email. Only if double opt-in is switched off in Mailchimp do you switch it off in the extension as well, with the skipDoubleOptIn setting; the documentation advises always using it. In the EU, it is also the usual way to demonstrate consent under Article 7(1) GDPR.

A fourth problem concerns servers behind a proxy. The extension only reaches the Mailchimp API if the proxy and port are entered in the extension configuration; there is also an option to force the connection to IPv4. Without these settings, no signup reaches Mailchimp, and TYPO3 does not keep the addresses either.

The extension stops at TYPO3 v10, current versions call for a direct API integration

The mailchimp extension in the TER was last released in January 2021 (version 3.2.0) and supports TYPO3 v9 and v10; there is no release for newer TYPO3 versions. Since Mailchimp API v3 is stable and well documented, Gosign recommends a direct API integration without an extension dependency for current TYPO3 projects. A custom service class in a dedicated TYPO3 package that talks to the Mailchimp API directly needs less maintenance than a community extension and can be tailored precisely to the project’s requirements. If newsletter content is to come from TYPO3, that also belongs in this integration; for this, Gosign maintains an email template set that renders the most common content elements in an email-compatible way.

Companies planning to stay with Mailchimp for the long term should also evaluate Mailchimp webhooks. Instead of polling for data at regular intervals, Mailchimp actively sends events (signup, unsubscribe, bounce) to a TYPO3 endpoint. That cuts sync latency from minutes to seconds and removes the load of periodic API queries.