Actually the requirement is to send Order notification and delivery notification email in our Magento store through Mailchimp. I have connected my magento store with Mai-chimp using extension with API
The contacts from Magento to Mail-chimp are synched in audience
But the order confirmation and Delivery notification email are not send so for that we need to use Mandrill?
Do I need to use Mandrill for sending email through Mailchimp? Because Mandrill is a paid service
I would suggest you to use Mageplaza SMTP, it's easy to use and configure and free as well.
Hope it helps !