UPDATE Oct 26th, 2018 – Microsoft is delaying the enforcement http://bit.ly/2D5uv3p
A quick reminder as the date is fast approaching: you must have moved to TLS 1.2 before October 31, 2018
It has been announced about a year ago (October 2017), all client-server and browser based communication with Office 365 services will use TLS 1.2
After October 31, 2018, if you are still using older TLS version (1.0 or 1.1), you will not be able to access your Office 365 services for client-server or browser-server communication.
If you need guidance to move to TLS 1.2, go there https://support.microsoft.com/en-us/help/4057306/preparing-for-tls-1-2-in-office-365