After Google officially stopped \support for the app earlier this month Inbox fans could still use the app using fresh installs of the archived version of the app’s apk files. This workaround for the app stop working recently as first noticed by Android Police, fresh installs of older app versions, such as 1.77, no longer let users sign in. The popular Google’s app Inbox is now no longer available.
Inbox was packed with tons of feature which Gmail still lacks. Feature like Bundles, Pinned Emails, Reminders etc. are still not implemented in the Gmail app.