Gmail is a free, advertising-supported email service offered as part of Google's G Suite, with 15GB of storage, color-coded inbox filters and unsend button.
Mandrill is a scalable and affordable email infrastructure service, with all the marketing friendly analytics tools they come to expect from MailChimp.
Google Cloud DNS is a scalable, reliable and managed authoritative Domain Name System (DNS) service running on the same infrastructure as Google. It has low latency, high availability and is a cost-effective way to make user applications and services available to users.
Mailchimp Transactional Email (formerly Mandrill) is a reliable, scalable and secure delivery API for transactional emails from websites and applications.