How to connect a WordPress signup form to your newsletter

A free WordPress plugin connects your site's forms to your Yellaro newsletter. You copy your Integration token and numeric list ID from your dashboard, paste them into the plugin, and newsletter signups flow straight into your list. There's no API user to set up and no per-subscriber fee — it's built on the open-source Listmonk, billed flat by emails sent.

This works with any WordPress site. It takes about five minutes, and the only things you copy are already waiting for you on the Integrations page of your dashboard.

If your site isn't on WordPress, skip the plugin — see add a signup form to any website for the plain-HTML approach instead.

Step 1: Copy your connection details

Open your Yellaro dashboard and go to Integrations. Everything you need is already there — you don't create an API user (Yellaro sets up a scoped one for you). Copy these four values:

• Listmonk URL — your instance URL, with no trailing slash (e.g. https://yoursite.yellaro.com)
• API username — this is integrations
• API token — click Show API token to reveal it, then copy it
• List ID — the small numeric ID next to your list, labelled List ID (WordPress)

That last point matters: the WordPress plugin uses the numeric List ID (like 3), not the long List UUID. The dashboard shows both per list and labels which is which — grab the one marked for WordPress.

Keep the token somewhere handy in a password manager. You'll see why in the gotcha below.

Step 2: Install the plugin

In your WordPress admin, go to Plugins → Add New and search for "Integration for listmonk" — it's the one by post-duif. Install and activate it. It's free and open source.

Step 3: Enter your connection details

Go to Settings → Integration for listmonk and fill in the values from Step 1:

• Listmonk server URL — your Listmonk URL, no trailing slash
• Listmonk API username — integrations
• Listmonk API access token — the token you copied
• List ID — the numeric ID from your dashboard

Save.

Step 4: Wire up a signup form (WPForms)

If you don't already have a newsletter form, create one with WPForms (the free version is fine):

1. WPForms → Add New, and choose the "Newsletter Signup Form" template (or build one with at least Name and Email fields)
2. Save the form and note its form ID
3. Back in Settings → Integration for listmonk, enable the WPForms component and enter that form ID

Now, when someone submits the form, their email and name go straight to your Yellaro list. If the list is double opt-in, Listmonk emails them a confirmation link automatically.

Step 5 (optional): WooCommerce checkout opt-in

Running a WooCommerce store? You can let customers opt into your newsletter at checkout:

1. In Settings → Integration for listmonk, enable the WooCommerce component
2. Set the opt-in checkbox text customers will see
3. Save

After checkout, customers who ticked the box are added to your list. WooCommerce opt-in skips double opt-in — they consented during a real transaction, so no second confirmation is needed.

Step 6: Test it

Submit your form with a test email you can check. Open Subscribers in your Listmonk admin — the new entry should appear within a few seconds. On a double opt-in list it starts as unconfirmed until they click the confirmation link.

If nothing shows up, the two most common causes are a wrong List ID (make sure it's the numeric one, not the UUID) and a token typo — re-copy both from the dashboard and try again.

A gotcha worth knowing about

When you go back to edit any plugin setting later — changing the list ID, updating the form ID, anything — the API access token field shows up blank, with a "Leave blank to keep the current token" style hint underneath.

In practice that hint can bite you: saving the settings page with the token field empty can wipe your stored token, and the plugin then fails silently. Your form still says "Thanks for signing up" to visitors, but nothing reaches your list.

The fix is simple: every time you save the plugin settings, re-paste your API token first. This is why Step 1 said to keep it in a password manager — it's one copy-paste away. This is a quirk of the plugin's UI, not a problem on the Yellaro side.

Why this is safe: a tightly scoped token

Here's the reassuring part. The Integration token you pasted into WordPress isn't a full-access key. Yellaro's Integration API user is scoped: it can only

• add subscribers to your lists, and
• read your list of lists.

That's it. It cannot send campaigns, change your settings, delete data, or touch your account. So unlike a generic Listmonk API user (which typically has broad admin rights), even if this token were somehow exposed, the blast radius is small — someone could add subscribers, nothing more. And if you ever want it changed, we can rotate it for you.

That's a deliberate design choice: the credential that lives on your public-facing website is the least-powerful one we can give you.

Not on WordPress?

If your site runs on Squarespace, Wix, Webflow, plain HTML, or anything else, you don't need this plugin — you can paste a small HTML form that posts directly to your subscription endpoint. See how to add a newsletter signup form to your website.