Kiwi for Gmail - Dedicated Gmail client with clean integration of Google Calendar, Contacts, Google Drive, and...
Polymail - Native email app for email productivity.
Streak - Manage customers inside Gmail
Canary Mail - Privacy-aware email app for Mac & iOS
Shift - Shift is the ultimate email client for managing Mail, Calendar, Drive, Slack, Asana, Jira, Evernote, and all your other favourite apps
Nylas Mail - The Nylas Cloud API powers your application with email, calendar & contacts features. Built-in features for better email, calendar, and contact management.