Use your Mandrill Account to Send Customer.io
Mandrill is designed for transactional messages only
Customer.io supports using your own Mandrill account to send email with zero loss in functionality. To do this, there are two places you’ll need to change settings:
1. In Customer.io
Configure your SMTP settings
First, head to Workspace Settings -> Email -> Custom SMTP Settings and click the Add Custom SMTP Server button:


Then add in your Mandrill settings (you can find those here)


Field | Value |
---|---|
Address | smtp.mandrillapp.com |
Port | 2525 |
Authentication | Login |
User name | [Your SMTP User Name] |
Password | [Your SMTP Password] |
When you save your settings, we’ll start sending emails through your Mandrill account.
Ensure that your unsubscribe link works
If you’re using the Customer.io unsubscribe, then everything will continue to work. If you’d prefer to use the Mandrill-provided unsubscribe you’ll want to add their unsubscribe link to your emails or layouts. You’ll need to make one change to ensure it processes. Also, add class=“untracked” to the link, like this:
<a href="*|UNSUB:http://mywebsite.com/unsub|*" class="untracked">Unsubscribe.</a>
Please note that if you’re using the Mandrill unsubscribe, those unsubscribes will not be tracked in Customer.io. They’ll only be tracked in Mandrill.
2. Mandrill
Point Mandrill’s webhooks at Customer.io
Go to the Mandrill webhooks page and click “Add a Webhook”.
From there, check these events:
- Message Is Sent
- Message Is Bounced
- Message Is Marked As Spam
- Message Is Rejected
- Message Is Delayed
- Message Is Soft-Bounced
In the “Post To URL” field, enter either https://track.customer.io/mandrill/events
if your account is in the US region or https://track-eu.customer.io/mandrill/events
if your account is based in the EU.
Use the correct URL for your region
track-eu
. We redirect traffic from US endpoints to EU-based accounts, however the traffic still passes through US servers and data may be logged in the US.
Click Create Webhook to save.
Disable CSS inlining
If you’re using the drag-and-drop email editor or our own CSS pre-processing Mandrill’s CSS inlining can interfere with our own, so we recommend disabling it. To do so, visit the Mandrill Sending Defaults page and make sure the Inline CSS Styles In HTML Emails option is disabled.
You can also disable Mandrill’s CSS inlining on a per-message basis by adding a custom X-MC-InlineCSS header to your email:
Success!
Your account is now set up to send email through Mandrill. If you have any questions or feedback about setting this up, just get in touch and we’ll be happy to help!