Nylas Mail - The Nylas Cloud API powers your application with email, calendar & contacts features. Built-in features for better email, calendar, and contact management.
Polymail - Native email app for email productivity.
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
New Gmail - The new version of Gmail web
MailClark - The Slack bot for external communications
Airmail for iOS - One of the best Mac email clients, now on iPhone