Canary Mail can show you the number of unread emails in your inbox on the app icon. You can enable the Notification Badges via the device settings.
On macOS devices, you will find this in System Preferences > Notifications > Canary mail > Check Badge app icon.
On iOS, you will find this in device Settings > Notifications > Canary > Toggle ON Badges.
On Android, you will find this in device Settings > Notifications > Canary > Toggle ON Badges.
