Microsoft Flags Potential Mail Disruption For Some Office 365 And Exchange 2013 Customers

Microsoft has warned that some customers using a hybrid of Office 365 and Exchange 2013 for its mail service may not receive their emails after the vendor renews its Office 365 transport layer security (TLS) certificate in April. The company has provided instructions on how to remediate this. Here are the details.

Microsoft’s Office 365 TLS certificate is set to expire soon and the company is renewing it on April 15. The certificate is used by Office 365 to provide TLS encryption between the cloud productivity suite and external Simple Mail Transfer Protocol (SMTP) servers. The renewed certificate comes with a few changes to improve security but can potentially stop mailflow between Office 365 and on-premise Exchange Servers.

If your organisation uses a hybrid deployment of Office 365 and Exchange 2013, you’ll be affected by the change if:

  • 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 and have not re-run the Hybrid Configuration wizard

If you are affected by the change, you should move to fix this as soon as possible. Microsoft’s Hybrid Configuration wizard can help you automatically configure your Exchange servers to work with the new TLS certificate:

  1. Download the latest cumulative update on at least one of your servers here, if you haven’t already done so.
  2. Download the Hybrid Configuration wizard and follow the instructions.

If you need to configure the Exchange servers manually:

  1. open the Exchange Management Shell on each of your Exchange 2013 servers
  2. Run the following commands:

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

    Set-ReceiveConnector -Identity $rc.Identity -TlsDomainCapabilities

    [Via Microsoft TechNet Blog]

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