Mailchimp Transactional Email (formerly Mandrill) is a reliable, scalable and secure delivery API for transactional emails from websites and applications.
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.
Salesforce.com, Inc. is an American cloud computing company headquartered in San Francisco, California. Though its revenue comes from a customer relationship management (CRM) product, Salesforce also sells commercial applications of social networking through acquisition and internal development.
Salesforce Heroku is part of the Salesforce Platform, enabling enterprises to store and leverage customer data in Salesforce for full-cycle CRM engagement.