Step-by-step guide to setting up Mailchimp (formerly Mandrill) with OneSignal for transactional email delivery. Includes domain configuration, API key setup, email testing, and subscriber management.
This guide is for users who already have a Mailchimp account and want to integrate it with OneSignal. If you don’t have a Mailchimp account, consider using OneSignal Email instead.
Go to the Mailchimp Transactional Email Domains page and add your domain if it hasn’t been added already.
Add domain
After adding your domain:
View DKIM/SPF Setup Instructions
Update your DNS records with your DNS provider. Follow Mailchimp’s setup guide if needed.
Mailchimp may take up to 48 hours to verify your domain. You’ll receive a confirmation email once complete.
In the Transactional Email Settings, click + New API Key.
Create API Key
You can name it something like OneSignal API Key
.
Name the API Key
Once created:
Copy the API key and SMTP Username
Treat your API key like a password — keep it secure and never share it.
Enable the following permissions to ensure compatibility with OneSignal:
API Key Permissions
Enable Email Messaging
Select Mailchimp and enter credentials
Configure Mailchimp email settings
Configure default sender info
Go to OneSignal > Messages > Email and click New Email.
Send Test Email
You should receive your test email shortly.
Having issues? Check the Email FAQ or email support@onesignal.com
.
For faster assistance, include:
If you are generating an API key from the main Mailchimp account dashboard:
Open profile menu
Navigate to Account & Billing
Access API Key section
Create a new API key
Generate key
Copy key to clipboard
✅ Email setup complete!
Next steps: