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Exchange 2019 CU 15 Stuck | Well-Known Object Error

Prepare AD Fails While Upgrading the Exchange 2019 CU 15

Vikas JakhmolaLast Updated: March 5, 2025

479 3 minutes read

How to fix Exchange well-known object error

Table of Contents

Exchange CU 15 fails with Well-Known Object Error While Prepare/AD

Microsoft Exchange 2019 CU 15 is the latest Exchange CU update released on 10 Feb 2025

This rollup update is highly recommended for all Exchange 2016 and 2019 users.

Though it is straightforward for the Exchange Admins to install the latest Exchange CU updates

However, sometimes it can be challenging to update it.

As you already know, you must prepare the schema and AD before installing the latest CU.

What if you cannot install this Microsoft Exchange and encounter an error?

In this article, we will know if a Prepare/AD fails while installing the CU 15.

Or you may face an error related to well-known object entry.

Why this Well-Known Object Error Occurs

Well-known objects are specific entries in AD on which Microsoft Exchange functionality depends, like security groups, recipient management, etc.

You may see the following error while preparing AD

The following error was generated when "$error.Clear();
initialize-ExchangeUniversalGroups -DomainController
$RoleDomainController -ActiveDirectorySplitPermissions $RoleActiveDirectorySplitPermissions

" was run:
"Microsoft.Exchange.Management.Tasks.InvalidWKObjectException: The well-known object entry

B:32:DB72C41D49580A4DB304FE6981E56297:CN=Recipient Management\0ADEL:16ebfda4-c02f-449b-90e7-cfe90995d271,CN=Deleted
Objects,DC=techijack,DC=com on the otherWellKnownObjects attribute in the container object CN=Microsoft
Exchange,CN=Services,CN=Configuration,DC=techijack.com,DC=com points to an invalid DN or a deleted object. Remove the
entry, and then rerun the task.
at Microsoft.Exchange.Configuration.Tasks.Task.ThrowError(Exception exception,
ErrorCategory errorCategory, Object target, String helpUrl)

Exchange setup needs the proper access to these well-known objects within Active Directory.

If these objects are deleted or corrupted, but still traces left in the Active Directory.

You will get the error related to Well-Known Object entry.

Without fixing this error, you may not be able to prepare AD.

Therefore, without preparing AD, you will not be able to install the latest cumulative update 15 on your Exchange Server.

How to Fix Microsoft Exchange Well-Known Object Error

There are two approaches to fix this issue.

Finding the related Well-known Object and deleting them with the help of ADSIEdit tool

This method is not recommended, if you delete any other by mistake

You may lose some important configuration and also break your Exchange Server.

Another method is to run the tested script to find this entry and safely remove it.

This script searches for the related entries and removes them from AD if they are already deleted.

You may download the following script and paste it into a Notepad

# Get Microsoft Exchange Container
$objDE = New-Object System.DirectoryServices.DirectoryEntry
$ExchangeDN = [string]::Concat("LDAP://CN=Microsoft Exchange,CN=Services,CN=Configuration,", $objDE.distinguishedName)
$objCN = New-Object System.DirectoryServices.DirectoryEntry($ExchangeDN)

$gp = [Reflection.Bindingflags]::GetProperty

# get otherWellKnownObjects Collection
$objCol = $objCN.otherWellKnownObjects
$delCount = 0

# Walk though the Collection backwards (always do that when deleting items)
for ($i=$objCol.Count-1; $i -ge 0; $i--)
{
    $objWKO = $objCol[$i]
    $objType = $objWKO.GetType()
	# Get the distinguishedName
	$DNString = $objType.InvokeMember("DNString", $gp, $null, $objWKO, $null)

    $BV = $objType.InvokeMember("BinaryValue", $gp, $null, $objWKO, $null)
    $Guid = [GUID][System.BitConverter]::ToString($BV).Replace("-", "")

    Write-Host "DNString: $DNString"
    Write-Host "Guid: $Guid"

	# Check if the item was deleted
	if ($DNString.Contains("0ADEL"))
    {
        Write-Host "This is a Deleted Item" -foregroundcolor Red
        # Remove the item (WARNING: No Confirmation asked)
		$objCol.RemoveAt($i)
        Write-Host "Object Removed" -foregroundcolor Red
        $DelCount++
    }
}

# Did we delete something?
if ($DelCount -gt 0)
{
    Write-Host "Commiting Changes" -foregroundcolor Blue
    # Commit changes, remove this line if you just want to test
	# If you don't commit you will not delete anything
	$objCN.SetInfo()
}

Therefore, save this script by any name with the extension of .ps1

In our case, I have saved this PowerShell script by the name of run.ps1 in the script folder inside my C: drive

Now open the Exchange Management shell, navigate to the script folder and run the script run.ps1

Once you run the above script, it will remove the deleted objects from their respective location to commit changes.

You will see the result as below