Important Notice About Certificate Expiration for Exchange 2013 Hybrid Customers

Microsoft is making a change on April 15^th that will possibly break mail flow from your on-premises environment to the Office 365 platform.  

This will have no impact on you if you are not running Exchange in hybrid mode. Please see the full details below on who will be affected. 

Our team is standing by to assist you with this change if needed to ensure mail flow is not interrupted.  

If you’re running Exchange 2013 and you’ve configured a hybrid deployment with Office 365, this post contains important information that might impact you. Please evaluate this information and take any necessary action before April 15, 2016. 

On April 15, 2016, the Office 365 TLS certificate will be renewed. This certificate is used by Office 365 to provide TLS encryption between Office 365 and external SMTP servers. The new certificate, which will help improve the security of mail sent to and from Office 365, will be issued by a new Certificate Authority and it will have a new Issuer and Subject.

This change has the potential to stop hybrid mailflow between Office 365 and your on-premises Exchange servers if one of the following conditions applies to you:

• Your on-premises Exchange servers are running Exchange 2013 Cumulative Update 8 (CU8) or lower.
• You’ve upgraded the Exchange 2013 servers that handle hybrid mailflow to Exchange 2013 CU9 or higher. However, since upgrading to CU9, you HAVE NOT re-run the Hybrid Configuration wizard (either from the Exchange Admin Center or via the direct download link).

If one of the previous conditions applies to your organization, hybrid mailflow between Office 365 and your organization will stop working after April 15, 2016 unless you complete the steps below.

Note: This only affects hybrid mailflow. Regular mailflow and TLS encryption is NOT affected.

How to keep hybrid mail flowing (MUST be completed before 4/15/2016)

Let the new Hybrid Configuration wizard do it for you

You can use the latest Hybrid Configuration wizard (HCW) to configure your Exchange 2013 servers to work with the new TLS certificate. Just follow these steps:

1. If the Exchange 2013 servers handling hybrid mailflow are running Exchange 2013 CU8 or lower, follow the instructions in Updates for Exchange 2013 to install the latest cumulative update on at least one server.
2. After you install the latest cumulative update, download the new HCW application and run the wizard following the instructions here.

Note: For information on which releases of Exchange are supported with Office 365, see Hybrid deployment prerequisites.

Manual update

If you can’t upgrade Exchange 2013 to latest cumulative update right now (although we would like to remind you of our support policy), you can manually configure your servers to work with the new TLS certificate. On each Exchange 2013 server that’s used for hybrid mailflow, open the Exchange Management Shell, and run the following commands:

$rc=Get-ReceiveConnector |where {$_.TlsDomainCapabilities -like "**"}

Set-ReceiveConnector -Identity $rc.Identity -TlsDomainCapabilities "mail.protection.outlook.com:AcceptCloudServicesMail

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