Old Google+ versions and photo backup may stop working on May 20, 2018
This message was sent because you may have an older version of the Google+ app installed on one of your mobile devices. Effective May 20, 2018, Google+ for Android version 7.5 and older and Google+ for iOS version 5.0 and older will no longer work. Note that if you chose to have the photo backup setting enabled in Google+, your photos will no longer be backed up. Previously backed up photos will not be affected.
If you’d like to continue backing up your photos with Google, you’ll need Google Photos. If you already use version 1.25 or newer of the Google Photos app for Android or any version of the Google Photos app for iOS and the back up & sync setting is on, you're all set. If not, you can get the Google Photos app and make sure the back up & sync setting is on.