# Mandrill (Mailchimp Transactional)

Source: https://catalystgroup.gg/docs/email-delivery/mailer-mandrill/
Updated: 2026-10-19 · By Duane Garner

Connect CRM-NG SMTP to Mandrill, Mailchimp's transactional email service, with an API key and a verified sending domain.

This guide shows you how to send your WordPress email through Mandrill, the transactional email service that Mailchimp now calls Mailchimp Transactional Email. It suits businesses that already use Mailchimp for newsletters and want their website mail in the same family. Mandrill is an add-on to a paid Mailchimp account and has no free plan.

 

The **Mandrill** mailer sends through Mandrill's API with an API key. Mandrill refuses mail from domains you have not verified, so domain setup is part of the job.

 

## Before you start

 
- A Mailchimp account with the Transactional Email (Mandrill) add-on turned on. You sign in to Mandrill with your Mailchimp login.
- A domain you control, with access to its DNS records.
- Administrator access to your WordPress site.

 

## Step 1: Add and verify your sending domain

 
1. Sign in to Mandrill
  Go to `https://mandrillapp.com/` and sign in with your Mailchimp account. (In Mailchimp, the add-on is under the transactional email section of your account.)
2. Open Sending Domains
  Open **Settings → Domains → Sending Domains**.
3. Add your domain
  Enter the domain you send from and add it.
4. Prove ownership
  Mandrill asks you to verify that you own the domain, usually by adding a TXT record or by clicking a link sent to an address at that domain.
5. Publish DKIM and SPF
  Mandrill shows the DKIM and SPF details for the domain. Add them at your DNS provider, then press the test button next to each one until both show as valid.

 

See [Adding DNS records](https://catalystgroup.gg/docs/email-delivery/dns-records/) for help with DNS.

 

## Step 2: Create an API key

 
1. Open SMTP & API Info
  In Mandrill, open **Settings → SMTP & API Info** (the plugin's **Get API Key** link goes to `https://mandrillapp.com/settings/index/`).
2. Add a key
  Choose **+ New API Key** and give it a description such as your site name.
3. Copy it
  Copy the key. You can limit what the key may do, but it must be allowed to send messages.

 

> **Test keys:** Mandrill can create test keys that accept mail without delivering it. Make sure you use a normal key for the live site, or nothing will arrive.

 

## Step 3: Connect in CRM-NG SMTP

 
1. Choose the mailer
  In WordPress, open **CRM-NG SMTP → Settings → General** and set **Mailer** to **Mandrill**.
2. Paste the key
  Paste the key into **API Key**.
3. Set the sender
  Set **From Email** to an address on your verified sending domain and set **From Name**. Tick **Force From Email** so other plugins cannot use an unverified domain.
4. Save
  Press **Save Settings**.

 

## Send a test email

 

Open **CRM-NG SMTP → Tools → Email Test**, enter your address in **Send To**, and press **Send Email**. Mandrill's **Outbound → Activity** page shows the message and whether it was sent, rejected or bounced. See [Sending a test email](https://catalystgroup.gg/docs/email-delivery/send-a-test-email/).

 

The domain check on the test page looks for `spf.mandrillapp.com` in your SPF record.

 

## Troubleshooting

 
- The key is wrong, deleted, or the add-on is off: [Invalid API key](https://catalystgroup.gg/docs/email-delivery/error-invalid-api-key/) and [401 Unauthorized or Forbidden](https://catalystgroup.gg/docs/email-delivery/error-401-unauthorized-or-forbidden/)
- Mandrill rejects mail from an unverified or unsigned domain: [553 Sender address rejected](https://catalystgroup.gg/docs/email-delivery/error-553-sender-address-rejected/)
- The recipient is on Mandrill's rejection list after an earlier bounce or complaint: [Email address in suppression list](https://catalystgroup.gg/docs/email-delivery/error-email-in-suppression-list/)
- You ran out of sending credits or hit an hourly quota: [Email sending limit reached](https://catalystgroup.gg/docs/email-delivery/error-email-sending-limit/)
- Mandrill suspended the account: [Account blocked](https://catalystgroup.gg/docs/email-delivery/error-account-blocked/)
- Mail arrives in spam: [Emails landing in spam](https://catalystgroup.gg/docs/email-delivery/emails-landing-in-spam/)

 

## Related

 
- [Choosing a mail service](https://catalystgroup.gg/docs/email-delivery/choose-a-mailer/)
- [Adding DNS records: SPF, DKIM and DMARC](https://catalystgroup.gg/docs/email-delivery/dns-records/)
- [Verifying your DNS records](https://catalystgroup.gg/docs/email-delivery/verify-dns-records/)
- [Sender name, address and the Force settings](https://catalystgroup.gg/docs/email-delivery/sender-name-and-address/)
- [Debug events](https://catalystgroup.gg/docs/email-delivery/debug-events/)