Microsoft has reminded customers earlier this week that Microsoft Office 2013 is approaching its end of support next year, advising them to switch to a newer version to reduce their exposure to security risks.
“After five years of Mainstream Support, and five years of Extended Support, Office 2013 will reach the End of Extended Support on April 11, 2023. Per the Fixed Lifecycle Policy, after this date security updates for Office 2013 will no longer be available,” Microsoft told customers.
Also, connecting Office 2013 clients to Microsoft 365 might lead to performance or reliability issues because Office 2013 is no longer a supported client since October 2020.
https://learn.microsoft.com/en-us/deployoffice/endofsupport/microsoft-365-services-connectivity
https://www.impresscomputers.com/product-category/office-365-email-and-office/
Older Office versions not supported for connecting to Microsoft 365 services
Older Office versions not listed in the table might still be able to connect to Microsoft 365 services, but that connectivity isn’t supported.
In practical terms, what this means is that these older Office versions might not be able to use all the latest functionality and features of Microsoft 365 services. In addition, over time, these older versions might encounter other unexpected performance or reliability issues while using Microsoft 365 services. That’s because as we make improvements to Microsoft 365 services, we’re not taking into account or testing with these older Office versions.
We won’t take any active measures to block older Office versions from connecting to Microsoft 365 services if they’re in extended support and are kept up to date. For example, Office 2013 with Service Pack 1, which is in extended support until April 11, 2023.
Therefore, to provide the best experience with using Microsoft 365 services, we strongly recommend that you move off older Office versions to versions supported for connecting to Microsoft 365 services.
Upgrade resources available to administrators
We recommend that you upgrade older Office clients to a subscription version of the Office client, such as Microsoft 365 Apps for enterprise. The most up-to-date subscription versions of the Office client are always supported connecting to Microsoft 365 services.