Today, the Exchange Team released the June updates for Exchange Server 2013 and 2016. Like the previous Cumulative Updates for these Exchange versions, Exchange 2013 CU17 and Exchange 2016 CU6 require .NET Framework 4.6.2.; NET Framework 4.7 has been tested by the Exchange team, but is still unsupported until further notice.

Exchange 2016 CU6 contains much awaited feature enhancements:

• Sent Items Behavior Control. The implementation of Sent Items behavior in Exchange 2016 CU6 won’t be backported to earlier Exchange versions, as these have their own implementation.
• Original Folder Item Recovery. This feature won’t be backported to previous versions of Exchange as well.

Apart from DST changes, check the lists below for changes contained in these updates.

Exchange 2016 CU6 fixes:

• KB4024658 FIX: The EAS web.config file is not updated on the CAFE server during a build-to-build upgrade
• KB4024654 POP/IMAP clients can’t log on with NTLM when Alias and SamAccountName are different in Exchange Server 2016
• KB4024653 Active Monitoring probes fail when you use a new accepted domain as the default domain in Exchange Server 2016
• KB4024652 Repeated IMAP SEARCH BODY requests may not return newly delivered messages in Exchange Server
• KB4024651 The “MessageRetrievalMimeFormat” setting isn’t honored for plain text-only email messages in IMAP in Exchange Server
• KB4024650 Emoji is displayed as question marks in iOS clients in an Exchange Server environment
• KB4024649 The Read or Unread flag isn’t synchronized correctly after you turn off an ActiveSync device overnight in Exchange Server
• KB4024648 FIX: A new contact created in OWA may be merged into an existing contact on Exchange Server 2016

• KB4024652 Repeated IMAP SEARCH BODY requests may not return newly delivered messages in Exchange Server
• KB4024651 The “MessageRetrievalMimeFormat” setting isn’t honored for plain text-only email messages in IMAP in Exchange Server
• KB4024650 Emoji is displayed as question marks in iOS clients in an Exchange Server environment
• KB4024647 “The property is too long” error when you update the “Department” field of user mailbox in Exchange Server 2013
• KB4024646 “Insufficient access rights” error when you run setup.exe as member of “Delegated Setup” group in Exchange Server 2013

Notes:

• Exchange 2016 CU6 includes schema changes, but Exchange 2013 CU17 does not. However, Exchange 2013 CU17 may introduce RBAC changes in your environment. Where applicable, use setup /PrepareSchema to update the schema or /PrepareAD to apply RBAC changes, before deploying or updating Exchange servers. To verify this step has been performed, consult the Exchange schema overview.
• When upgrading your Exchange 2013 or 2016 installation, don’t forget to put the server in maintenance mode when required. Regardless, setup will put the server in server-wide offline mode post-analysis, before making actual changes.
• Using Windows Management Framework (WMF)/PowerShell version 5 or later on anything earlier than Windows Server 2016 is not supported. Don’t install WMF5 on your Exchange servers running on Windows Server 2012 R2 or earlier.
• NET Framework 4.7 is being tested by the Exchange Team, but is not supported until further notice.
• Customers who have deployed Exchange in Hybrid or use Exchange Online Archiving need to stay current, or at least run the prior Cumulative Update version.
• When using Exchange hybrid deployments or Exchange Online Archiving (EOA), you are required to stay at most one version behind (n-1).
• If you want to speed up the update process for systems without internet access, you can follow the procedure described here to disable publisher’s certificate revocation checking.
• Cumulative Updates can be installed directly, i.e. no need to install RTM prior to installing Cumulative Updates.
• Once installed, you can’t uninstall a Cumulative Update nor any of the installed Exchange server roles.
• The order in which you upgrade servers with Cumulative Updates is irrelevant.

Caution: As for any update, I recommend to thoroughly test updates in a test environment prior to implementing them in production. When you lack such facilities, hold out a few days and monitor the comments on the original publication or forums for any issues.