https://www.oldversion.com.de/android/com-google-android-apps-inbox/com-google-android-apps-inbox-1-6-90778564-5619879/
Download Inbox by Gmail 1.6_(90778564)-5619879 for Android - OldVersion.com
Find and download older versions of software for Windows, Mac, Linux, Android, and games. Because newer isn't always better.
inbox by gmail
https://en.wikipedia.org/wiki/Inbox_by_Gmail
Inbox by Gmail - Wikipedia
inbox by gmailwikipedia
https://www.androidauthority.com/no-invite-required-for-inbox-by-gmail-anymore-new-features-added-612113/
No invite required for Inbox by Gmail anymore, new features added
May 28, 2015 - Inbox by Gmail is out of beta and does not need an invite anymore, and has a slew of new features introduced to the mix.
inbox by gmailno invitenew featuresrequired
https://www.emailblasteruk.com/blog/inbox-by-gmail-and-email-marketing/
Inbox By Gmail and Email Marketing
Jan 15, 2015 - How will Inbox by Gmail and Email Marketing be affected? We discuss how Inbox by Google will impact on your email marketing. Will open rates decrease?
inbox by gmailemailmarketing