UPDATE, Sept. 6: Microsoft has updated its Office support statement. Read Helping customers shift to a modern desktop:
Office 2016 connectivity support for Office 365 services
In addition, we are modifying the Office 365 services system requirements related to service connectivity. In February, we announced that starting October 13, 2020, customers will need Office 365 ProPlus or Office 2019 clients in mainstream support to connect to Office 365 services. To give you more time to transition fully to the cloud, we are now modifying that policy and will continue to support Office 2016 connections with the Office 365 services through October 2023.
What a difference a word makes.
On April 20, 2017 the Office Blog wrote an article about Office 365 system requirements changes for Office client connectivity. It references the updated System Requirements for Office, which states:
“Effective October 13th, 2020, Office 365 will only allow Office client connectivity from subscription clients (Office 365 ProPlus) or Office perpetual clients within mainstream support to connect to Office 365 services. (Please refer to the Microsoft support lifecycle site for Office mainstream support dates.)”The blog says this "will make it easier for enterprises to deploy and manage Office 365 ProPlus". Perpetual clients is the term for traditional MSI-installed Office, usually from media or a UNC share.
The problem is the word "allow" should be "support". "Allow" implies that Microsoft will actively block all connectivity from Office clients that are not in mainstream support. According to the Microsoft Lifecycle Policy, Microsoft Office 2016 mainstream support ends 10/13/2020.
Even the beginning of the System Requirements for Office is at odds with the statement above. It says:
"Office 365 is designed to work best with Office 2016, Office 2013, and Office 2016 for Mac. Previous versions of Office, such as Office 2010, Office 2007, and Office for Mac 2011 may work with Office 365 with reduced functionality."
This is the traditional support statement we've seen for years. You can continue to use legacy versions of Office with Office 365, you just can't get support for it. If it works, great. If it doesn't, upgrade.
Of course, Microsoft's and my own recommendation is to use the latest and greatest versions of Office. In particular, you should be using Office 365 ProPlus, especially for users who use Office 365. But there are a lot of enterprise and SMB customers who still buy Office using perpetual licenses. They like the fact that they own it and don't have to pay for a monthly subscription per user. Some hybrid customers have a large number of seats on-prem, without having to pay for Office 365 ProPlus licenses for these users. Some SMB customers have Office 365 plans that don't include Office 365 ProPlus.
Recently, I've heard from customers that Microsoft Office 365 Support is telling them that Office 2016 won't be able to connect to Office 365 after October 13, 2020 and are referencing this support statement. That's heavy-handed fear mongering and it has to stop.
I'm currently in conversations with the Exchange product group about the new support statement. We agree that the word "allow" should be changed to "support", but they don't control the website or message - the Office Team does. We're still in talks, trying to get the word changed. I'll let you know here how that goes...