As previously communicated (MC124102 in Oct 2017, MC126199 in Dec 2017 and MC128929 in Feb 2018), we are moving all of our online services to Transport Layer Security (TLS) 1.2+ to provide best-in-class encryption, and to ensure our service is more secure by default.
[How does this affect me?]
As of October 31, 2018, Office 365 will no longer support TLS 1.0 and 1.1. This means that Microsoft will not fix new issues found in the client, device or service that connects to Office 365 using TLS 1.0 and 1.1.
Please note: TLS 1.0 and 1.1 will continue to function but are no longer supported. We will provide additional notification prior to retiring TLS 1.0 and 1.1 completely.
[What do I need to do to prepare for this change?]
You should ensure that all client-server and browser-server combinations use TLS 1.2 (or a later version) to maintain connection to Office 365 services. This may require you to update certain client-server and browser-server combinations.
Where possible, Microsoft recommends that you remove all TLS 1.0/1.1 dependencies in your environments and that you disable TLS 1.0/1.1 at the operating system level.
Begin your migration to TLS 1.2+, today.