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.
SendGrid cloud-based email infrastructure relieves businesses of the cost and complexity of maintaining custom email systems. SendGrid provides reliable email delivery, scalability and real-time analytics along with flexible API's that make custom integration a breeze.
Zendesk is a cloud-based customer service software solution trusted by over 40,000 organizations worldwide. Companies such as Groupon, Box, and Zappos are using Zendesk to lower costs, raise productivity, and increase customer satisfaction.
Mailchimp Transactional Email (formerly Mandrill) is a reliable, scalable and secure delivery API for transactional emails from websites and applications.
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.