Mailchimp Transactional is a paid add-on to a Mailchimp account — it's separate billing from the Marketing side. Here's the full path from zero to a working API key.

Step 1 — Have (or create) a Mailchimp account

Sign up at mailchimp.com/signup if you don't already have one. The free tier is fine for this — you only need a paid Marketing plan if you want to use subaccounts and some advanced features on the Transactional side.

Step 2 — Enable Transactional Email on the account

Once logged into Mailchimp:

  1. Click your profile icon (top right) → Account & billing.
  2. Open the "Transactional Email" tab.
  3. Choose a plan and buy at least one block of sends. Transactional is priced in "blocks" — 25,000 emails is the smallest block (around $20 at the time of writing, but check the current pricing on the page). You have to buy the first block before the dashboard unlocks.
  4. Click "Launch App". This opens the Mandrill dashboard at mandrillapp.com — the Transactional side of Mailchimp still uses the old Mandrill URLs.
Why it's paid-only: Transactional email has strict anti-abuse requirements (verified domains, reputation monitoring, dedicated IP warmup), so there isn't a free tier the way there is for newsletters.

Step 3 — Generate an API key

  1. In the Mandrill dashboard, go to Settings (gear icon, top right).
  2. Find the SMTP & API Info section.
  3. Click New API Key. Optionally give it a description like "elegantwork demo".
  4. Copy the key — it's a long random string. This is the only time it'll be shown in full; treat it like a password.

Step 4 — Paste it into config.php

Open config.php in this demo and replace the placeholder:

define('MANDRILL_API_KEY', 'md-xxxxxxxxxxxxxxxxxxxxxx');

Then reload Step 1: Ping. If it returns {"PING": "PONG!"} you're connected.

Step 5 — Verify a sending domain (required before you can send email)

You can manage the allowlist without this, but the moment you want to actually send mail (Step 5 of the demo), the from_email must be on a domain you've verified. In the Mandrill dashboard:

  1. Settings → Sending Domains.
  2. Add your domain (e.g. elegantwork.co.za).
  3. Publish the three DNS records Mandrill gives you:
  4. Hit Test DNS Settings in Mandrill until all three go green.

Then update config.php:

define('DEFAULT_FROM_EMAIL', 'noreply@elegantwork.co.za');
define('DEFAULT_FROM_NAME',  'Elegant Work');

Security notes

Never commit config.php to a public repo. For a production setup, move the key into an environment variable or a file outside the web root and require it from there. This demo keeps it inline for simplicity, but add config.php to your .gitignore if you're versioning this folder.

→ Once you've pasted the key, continue to Step 1: Ping