Today I had to install new Exchange 2016 CU on a customer’s exchange environment. Normally that is an easy going thing and I wouldn’t write an article about that.

However, by this customer I came across an installation problem during the update.


I was running like always my pre setup steps for suspending the cluster:

Suspend-ClusterNode –Name EX2016SRV1


After that, I disabled the database copy activation using this cmdlet:

Set-MailboxServer EX2016SRV1 –DatabaseCopyActivationDisabledAndMoveNow $true


Then I blocked the activation Policy using the following command:

Set-MailboxServer EX2016SRV1 –DatabaseCopyAutoActivationPolicy Blocked


And last but not least I needed to set the Exchange server in Maintrance mode:

Set-ServerComponentState EX2016SRV1 –Component ServerWideOffline –State InActive –Requester Maintenance


Note: Don’t forget to disable temporary the Anti Virus scanner and reboot the server before starting the setup.


After these pre-setup tasks, I was ready to mount the ISO file and start the update using:

setup /m:upgrade /IAcceptExchangeServerLicenseTerms


Good so far… Till here everything went fine and as expected. During the update Microsoft started working on the Mailbox roles. The Transport service and Client Access service had no problem and completed successfully. The same with the Language Files and Restoring Services.

However, next task was about Unified Messaging service. Here I got after 90% the error below:

To understand the error, I opened the Event Viewer, for me personally it is a more easy way to read the error and to find the solution of the issue.


Checking the error message I found an issue, which could be the reason for the unsuccessful setup. By taking a closer look, I found this:

In my case that means, that by the installation of Exchange server 2016 the ISO file was mounted to the Drive Letter D:\. After installing Exchange, the ISO was dismounted and the D:\ Letter was used for the Mailbox databases.

Now by installing the newest CU, the mounted ISO got the letter E:\ and the uninstall of the old MSI was not possible, because the path of it doesn’t exists anymore.

After knowing this history, the solution in my case was easy. I have created on the D:\ Partition a Folder called “en” (Note: the name can be different, it depended about your language settings) and copied the UMLanguagePack.en-US.msi from the ISO to the new folder.

Now I restarted the setup and it went as expected without further errors to the end.


To finish the whole setup, there are now tree things left to do:

  1. Reactivate the Antivirus Software
  2. Reboot the Exchange server
  3. Disable the Maintenance:
Set-ServerComponentState EX2016SRV1 –Component ServerWideOffline –State Active –Requester Maintenance