As of October 13, 2020, Office 2016 for Mac and Office 2010 for Windows will reach their end of support. After that date, Microsoft will no longer provide technical support, bug fixes, or security updates for either version.

Microsoft will not take any active measures to block older versions of the Office client from connecting to Office 365 services, but these legacy clients may encounter performance and/or reliability issues over time.

If you’re using Office 2016 for Mac and Office 2010 for Windows, Contact your local IT Support person or the Help Desk (help.desk@utoronto.ca) to upgrade to latest version.

More details can be seen at: https://techcommunity.microsoft.com/t5/office-end-of-support-blog/ask-microsoft-anything-upcoming-changes-to-office-support-may-5/ba-p/1322539.