Preparing for the mandatory use of TLS 1.2 in Office 365
As of October 31, 2018, Microsoft Office 365 will no longer support TLS 1.0 and 1.1.
By October 31, 2018, all client-server and browser-server combinations should use TLS version 1.2 (or a later version) to ensure connection without issues to Office 365 services. This may require updates to certain client-server and browser-server combinations. Read More.