Released: September 2020 Quarterly Exchange Updates

Published Sep 15 2020 07:00 AM 45K Views

Today we are announcing the availability of quarterly servicing cumulative updates for Exchange Server 2016 and 2019. These updates include fixes for customer reported issues as well as all previously released security updates. 

A full list of fixes is contained in the KB article for each CU, but we wanted to highlight the following.

Calculator Updates

A few bug fixes are included in this quarterly release of the Exchange Sizing Calculator. The calculator was updated to ensure CPU usage was correctly calculated in some scenarios and an issue in which when the second node was removed in worst case failure scenario, and which resulted in a zero transport DB size when Safety Net was enabled was also resolved.

Surface Hub Teams and Skype Experience

When Exchange Server 2019 CU5 and Exchange Server 2016 CU16 were released we subsequently discovered issues with Surface Hub devices configured with on-premises mailboxes. In those cases if both the Teams and Skype for Business clients were installed side by side, the Surface Hub would pick the incorrect client when joining meetings. The CU’s issued today resolved these issues.

Release Details

The KB articles that describe the fixes in each release and product downloads are available as follows:

Additional Information

Microsoft recommends all customers test the deployment of any update in their lab environment to determine the proper installation process for your production environment. For information on extending the schema and configuring Active Directory, please review the appropriate documentation.

Also, to prevent installation issues you should ensure that the Windows PowerShell Script Execution Policy is set to “Unrestricted” on the server being upgraded or installed. To verify the policy settings, run the Get-ExecutionPolicy cmdlet from PowerShell on the machine being upgraded. If the policies are NOT set to Unrestricted you should use the resolution steps in here to adjust the settings.

Additionally, if you plan to install any Cumulative Update using the unattended option with either PowerShell or Command Prompt, make sure you specify either the full path to the setup.exe file or use a “.” in front of the command if running it directly from directory containing the update. If you do not the Exchange Server Setup program starts and may indicate that it completed successfully, though it has not. Read more here.

Reminder: Customers in hybrid deployments where Exchange is deployed on-premises and in the cloud, or who are using Exchange Online Archiving (EOA) with their on-premises Exchange deployment are required to deploy the currently supported cumulative update for the product version in use, e.g., 2013 Cumulative Update 23; 2016 Cumulative Update 18 or 17; 2019 Cumulative Update 7 or 6.

For the latest information on the Exchange Server and product announcements please see What's New in Exchange Server and Exchange Server Release Notes.

Note: Documentation may not be fully available at the time this post is published.

The Exchange Team

Senior Member


Senior Member

Are there any AD Prep or Schema changes needed between Exchange 2016 CU17 & the newly released CU18?

Occasional Contributor

Hello Microsoft ,


Thank you for the information. I believe we have to wait till the article is updated as getting page not found errors


@j_ware there are no Schema changes but objectVersion (Default) was increased to 13238 (2016) 13238 (2019) and objectVersion (Configuration) to 16218 (2016) 16755 (2019), so /PrepareAD is required.


Documentation will be available very soon. Stay tuned.


@Ajit Terdalkar yes, you're right. Stay tuned. They will be online very soon.

Occasional Contributor

Hello Lukas,


Links are accessible now  Thank you 

Frequent Visitor

I have downloaded Exchange 2019 CU7, when I do an update - there will be CU6 installed?
Is there a problem with this image? SW_DVD9_Exchange_Svr_2019_CU_7_MultiLang_Std_Ent_.iso_MLF_X22-38503.ISO
Why I start the GUI setup - there will be shown CU7, when I start the same setup with powershell, there will be shown CU6


I checked the image several times ...



New Contributor
@Lukas SasslKB4571788 for Exchange 2016 CU18 says: -
"If you are upgrading from Cumulative Update 13 for Exchange Server 2016 or a later cumulative update for Exchange Server 2016 to Cumulative Update 18 for Exchange Server 2016, then there’s no need to run the /PrepareAD.
However, in your comment above to J_ware, you are saying that: -
"objectVersion (Default) was increased to 13238 (2016) 13238 (2019) and objectVersion (Configuration) to 16218 (2016) 16755 (2019), so /PrepareAD is required"
Could you please clarify?

@sjhudson let me check that. I guess it's a mistake. 

Occasional Visitor

Is it required to reboot the server after upgrading CU 17 to 18?


Unattended setup does not mention this


@mp2884  - Thanks for reporting. We're investigating. 

Senior Member

@Martijn Westera yes, you will need to reboot after installing a CU.



We've checked this and it looks like you've run setup.exe by using PowerShell without using the full path or ".\" (as we've described it here in step 3:


When calling the setup.exe in PowerShell without executing using the full path or ".\" under its current directory, Exchange setup process seems to treat the Setup.exe based on environment variable, and the local Exchange installation path will be set as the "sourcedir" and you end up in the described behavior.


Please make sure to run setup.exe using the full path or ".\" to avoid this scenario.

Senior Member

@mp2884 @Lukas Sassl  I always use a "Run As Administrator" command prompt for running CU updates or any other Exchange installer, and also make sure all interactive powershell sessions are closed and no one else is logged on to the server; if someone else is logged on and has the exchange management shell open that will cause the install to fail.


@j_ware This is exemplary and highly recommended. Anyway - in the scenario described above setup is executed and at first glance it looks successful but after the setup process you're still on the same Exchange build because we don't use the new bits from the Exchange CU .iso due to the wrong "sourcedir". To avoid this, call setup.exe by using the full path in unattended mode: E:\setup.exe (PowerShell and/or cmd) or if you're in the same directory .\setup.exe (PowerShell only) should also do the job.

Frequent Visitor

Thanks for alle the replies - good to know ;)


@sjhudson We've removed the part from the KB that says that no /PrepareAD is required. It is definitely required to run /PrepareAD with this release for both versions - Exchange 2016 and Exchange 2019.



New Contributor


Performing the CU18 on Exchange 2016, I confirmed that the below must be done before starting the update 

Prepare Ad Organization

Setup.exe /PrepareAD /IAcceptExchangeServerLicenseTerms

Prepare All Domains

Setup.exe /PrepareAllDomains /IAcceptExchangeServerLicenseTerms


Schema ------> nothing has changed  15332

"Exchange Schema Version = " + ([ADSI]("LDAP://CN=ms-Exch-Schema-Version-Pt," + ([ADSI]"LDAP://RootDSE").schemaNamingContext)).rangeUpper


$RootDSE= ([ADSI]"").distinguishedName

([ADSI]"LDAP://CN=Microsoft Exchange System Objects,$RootDSE").objectVersion  

----> 13238


Verify with ADSI edit the Configuration, Services, Microsoft Exchange, OrgExchangename

ObjectVersion (Configuration) to 16218



Occasional Visitor

PDF preview is broken in OWA for mailboxes opened via "open another mailbox", e.g. shared mailboxes.

And if you try to download the PDF attachment, you are redirected to


There is also someone on reddit:


@kekslicht0815 thanks for bringing this up to our attention. We'll have a look at this.

Established Member

@Lukas Sassl @kekslicht0815 

We're experiencing the same problem after updating our servers to the newest CUs and we run 2016 and 2019 versions. Currently migrating all mailboxes to the new 2019 cluster.


Thanks @Dhiogo for letting us know. The behaviour is currently being investigated.

Senior Member

exactly the same issue with xlsx files - is there any temporary solution?

for example disable online viewing

Thank you 

Occasional Visitor

Trying to upgrade Exchange 2019 from base original version to CU7.  However, all the links to CU7 require Volume License Authorization and keys.  I have the original product key for Exchange 2019 but can not download the CU7.  Is there another place that I can download CU7 without using Volume License site?



Exchange 2019 can only be downloaded from the Volume License Center as announced here:

Senior Member

We are on Exchange 2016 cu14 (but I DID install .net 4.8).   Can I jump straight to the latest CU?  (I feel like somewhere I saw it was recommended not to go past 2 CU's ahead.) as in, I would need to go to cu16 and then to cu18?

Established Member

@Lukas Sassl 

Absolutely, Lukas. I will give a look right now.

Thank you for still hanging with us during this problem. Your help is much appreciated.

Occasional Visitor

@Lukas Sassl 

The workaround with OWA light works.

Some users struggle with adding the "?layout=light" at the right position, because OWA automatically also adds some parameters to the URL and without knowledge how URL-Parameters work, they have some difficulties and need more support from our helpdesk.

Regular Visitor

So to go from cu17 to cu 18 itis:

Setup.exe /PrepareAD /IAcceptExchangeServerLicenseTerms


and no schema or domain prep?

Occasional Visitor

It seems like the Exchange 2016 CU18 should have more patience coded into it.  Installation failed multiple times on one of my VMs with "cannot start service winmgmt on computer '.'".  In each case, the service was started when I looked.  It seems like the installer isn't waiting long enough for it to start.

Version history
Last update:
‎Oct 14 2020 10:44 AM