Gotcha! I think easiest way would be a. You'd configure Mailchimp details (api key etc) inside Courier's provider/integrations interface b. Invoke Courier API and Courier would route it to Mailchimp

["a" can be any integration Courier supports - so it could be Twilio for SMS for instance] ["b" changes based on how you invoke the API - so you could do send just an email via Mailchimp, send just an SMS via Twilio OR both email and SMS OR SMS if email fails and so on --- this logic is configurable via both UI and API]