There aren't too many new features in these CUs. The most important ‘feature' is that TLS 1.2 is now fully supported (most likely you already have TLS 1.2 only on your load balancer). This is extremely supported since Microsoft will support TLS 1.2 ONLY in office 365 in the last quarter of this year (see the An Update on Office 365 Requiring TLS 1.2 Microsoft blog as well).
Support for .NET Framework 4.7.1, or the ongoing story about the .NET Framework. The .NET Framework 4.7.1 is fully supported by exchange 2016 CU9 and Exchange 2013 CU20. Why is this important? For the upcoming CUs in three months (somewhere in June 2018) the .NET Framework 4.7.1 is mandatory, so you need these to be installed in order to install these upcoming CUs.
Please note that .NET Framework 4.7 is NOT supported!
If you are currently running an older CU of Exchange, for example Exchange 2013 CU12, you have to make an intermediate upgrade to exchange 2013 cu15. Then upgrade to .NET Framework 4.6.2 and then upgrade to Exchange 2013 CU20. If you are running exchange 2016 cu3 or CU4, you can upgrade to .NET Framework 4.6.2 and then upgrade to Exchange 2016 CU9.
If you are coming from a recent Exchange 2013 CU, there are no schema changes since the schema version (rangeUpper = 15312) hasn't changed since Exchange 2013 CU7. However, since there can be changes in (for example) RBAC, it's always a good practice to run the Setup.exe /PrepareAD command. For Exchange 2016, the schema version (rangeUpper = 15332) hasn't changed since Exchange 2016 CU7.
As always, check the new CUs in your lab environment before installing into your production environment!!
Exchange 2016 CU9 Information and download Links
- Exchange 2016 CU9 download: https://www.microsoft.com/en-us/download/details.aspx?id=56718
- Exchange 2016 CU9 KB article: https://support.microsoft.com/en-us/help/4055222/cumulative-update-9-for-exchange-server-2016
- Exchange 2016 CU9 UM Language Pack: https://www.microsoft.com/en-us/download/details.aspx?id=56715
Exchange 2013 CU20 Information and download Links
Exchange Server 2013 enters the Extended Support phase of product lifecycle on April 10th, 2018. During Extended Support, products receive only updates defined as Critical consistent with the Security Update Guide. For Exchange Server 2013, critical updates will include any required product updates due to time zone definition changes.
- Exchange 2013 CU20 download: https://www.microsoft.com/en-us/download/details.aspx?id=56717
- Exchange 2013 CU20 KB article: https://support.microsoft.com/en-us/help/4055221/cumulative-update-20-for-exchange-server-2013
- Exchange 2013 CU20 UM Language Pack: https://www.microsoft.com/en-us/download/details.aspx?id=56716