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Office 365 customers must have TLS 1.2 enabled before October 31

A quick Office 365 reminder as a critical date is fast approaching: you must have TLS 1.2 enabled before October 31, 2018.


Microsoft announced that in an effort to safeguard consumer communications against potential attacks and other TLS vulnerabilities, they will enforce the use of Transport Layer Security (TLS) Version 1.2 across all Microsoft Office 365 environments as of October 31, 2018. At this time, they will also discontinue support for TLS versions 1.0 and 1.1. What does this mean? After October 31, 2018, if you have not made the changes required for TLS 1.2 compatibility, you will not be able to access your Office 365 services. Office 365 customers don’t necessarily have to remove or disable TLS 1.0 and 1.1, Microsoft has just advised that those older protocols can’t be used with Office 365 services after the October deadline date.


What Does This Change to TLS 1.2 Affect?

Essentially, TLS 1.2 must be enabled on any system that interacts with Office 365. This includes web browsers, Outlook clients, and Lync or Skype for Business clients connecting to Office 365 Online environments. Also, Microsoft is urging customers with any on-premises infrastructure for hybrid scenarios (Exchange and Skype for Business) or Active Directory Federation Services to verify that their systems can support both inbound and outbound connections that use TLS 1.2.

How to Prepare

To prepare your environments for the upcoming TLS 1.2 change, there are three general scenarios to review and, if applicable to your organization, adequately plan and prepare for:

  1. PC browser/Outlook/Lync/Skype client connectivity to Office 365
  2. On-premises server integration with Office 365
  3. Third-party application integration with Office 365


A quick list of potentially affected systems includes:

  • Exchange Hybrid
  • Skype for Business Hybrid
  • Azure Active Directory Connect
  • Active Directory Federation Services
  • Polycom CX-series LPE phones
  • Windows Server 2008R2 and older
  • Windows 7 and older
  • .Net Framework


Cerium Networks can accurately assess if TLS 1.2 should be enabled on your systems used for communication with Office 365. We are here to help you avoid any interruption in Office 365 service when the end of October rolls around, so please contact us for assistance.

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