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
Clean Email - Clean Email is an online service that empowers you to take control of your mailbox.
Airmail for iOS - One of the best Mac email clients, now on iPhone
MailClark - The Slack bot for external communications