Windows 10 Mobile 10586.164 Rolling Out; Officially Ready for Windows Phone 8.1 Upgrade

Today, Microsoft is rolling out a new Windows 10 Mobile build for those who are on the Slow & Production builds using the Windows 10 Insiders Programme. This build is labeled as version 10586.164 which is a minor bump from 10586.122, but it comes with several important fixes, and update. What is even more significant about the build is that its going to retail i.e. this will be the first public release for other devices running Windows Phone 8.1

Note: Those running Lumia 550, 650, 950 XL and 950, and are on Fast Ring won’t see this update because you guys are on 14XXX branch (Redstone) while this is pre-Redstone.  Important changes in 10586.164:

• Improvements for the reliability of app notifications, including text messages and alarms not ringing as scheduled.
• Improvements for text message backup to reduce data and battery usage.
• Fixes for Microsoft Edge with address bar suggestions showing late or persisting during navigation, “Close all tabs” not closing all tabs, and Word Flow on the address bar not functioning as expected.
• Fix for a problem where the Microsoft account was not detected by the Outlook Mail, Outlook Calendar and People app. Attempting to add a new contact in this state caused the People app to crash for some users.
• Fix for a problem that caused the Wi-Fi connection to temporarily switch off after prolonged use for some users.
• Fix for a problem that caused first-party app updates to fail to install successfully for some users, leaving the apps in state where they cannot be launched.
• Improvements for battery usage, Bluetooth connectivity, and OS reliability.

If you are on Fast Ring, and Pre-Redstone, you will need to switch  RING to Slow or Production to get this update and then switch to fast ring again. Microsoft didn’t release this to Fast Ring users because it has small improvements, over .122 and mostly bug fixes.
Source: Microsoft Community