Use your Mandrill Account to Send Customer.io

Mandrill is designed for transactional messages only

Mailchimp’s acceptable use policy prohibits the sending of bulk emails—emails directed to multiple individuals with the same content—through Mandrill.

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/eventsif 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

If your account is based in the European Union (EU), make sure you use endpoints beginning with 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.

Mandrill Sending Options, with CSS inlining disabled and highlighted

You can also disable Mandrill’s CSS inlining on a per-message basis by adding a custom X-MC-InlineCSS header to your email:

Editing custom headers in the email editor

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!