Hiver - Manage Customer Support, Sales and Projects right from your Gmail inbox. Collaborate with Shared Labels, Shared Contacts, email notes, email reminders and email templates

Thunder Mail - Cheap and simple transactional emails API with Amazon SES

Clean Email - Clean Email is an online service that empowers you to take control of your mailbox.

PopcornNotify - Send simple emails and text messages from one API

Nylas Mail - The Nylas Cloud API powers your application with email, calendar & contacts features. Built-in features for better email, calendar, and contact management.

Inbox Ignite - Prevent your emails from going into spam