From October 13th, 2020 Microsoft will only support some Office versions with regard to the connection to Office 365 (or Microsoft 365). Although no active attempts are made to prevent the connection of the versions not mentioned, it is pointed out that performance and stability problems and increased security risk can occur on older clients. After October 15th, the infrastructure will be rebuilt and from now on TLS 1.2 will be used.
From October 13th, only the following versions will be supported with the cloud services, at least actively. Of course, Microsoft, therefore, recommends – if possible – to update older clients accordingly. The latest version is always available for the subscription variants.
The difference for Office 2016 is also pointed out: Since the Mac version has reached the “End of Support” status, it is no longer supported for the cloud connection either.
An expiration date has also already been set for Office 2016 and Office 2019: The Office versions mentioned should be supported until October 2023.