Exchange 2016 Error During Install: “Database is mandatory on UserMailbox. Property Name: Database”

As part of my migration project that I am currently working on which has been the talking point of most of my blog posts of late, it seems the saga of the 2010 > 2016 migration continues.

The story begins one windy Wednesday night after a tumultuous couple of days trying to nail down prerequisites and get Exchange 2016 to install,  I was sipping champagne from a straw celebrating my triumph and preparing to move onto the next phase setting up the DAG and getting the system mailboxes etc. moved when we had a catastrophic hard drive failure.

Sadly my nights of sipping champagne came to an abrupt end and I was left with a very broken Exchange 2016 server x2.  Fast forward to today and I am eagerly anticipating the end of the work day as my celebrations have begun again in earnest, I have just fixed up the last of the issues that I experienced as a result of the drive failure for Exchange.

This blog post details the process that I followed to resolve an error that I was receiving when attempting to reinstall Exchange 2016 after the uninstallation.  I had made the assumption that the uninstaller would remove any attributes / extensions etc. that were created as part of the install. This was not the case, in fact the uninstaller is rather reminiscent of my husband just leaving trails of his clothes behind him wherever he goes.  Needless to say I had to go in and manually clean up all traces of Exchange 2016 before I could continue on with the reinstallation.

The detailed error message that I was getting is as follows:

Error: The following error was generated when “$error.Clear();
if ($RoleIsDatacenter -ne $true -and $RoleIsDatacenterDedicated -ne $true)
if (Test-ExchangeServersWriteAccess -DomainController $RoleDomainController -ErrorAction SilentlyContinue)
$sysMbx = $null;
$name = “SystemMailbox{bb558c35-97f1-4cb9-8ff7-d53741dc928c}”;
$dispName = “Microsoft Exchange”;
Write-ExchangeSetupLog -Info (“Retrieving mailboxes with Name=$name.”);
$mbxs = @(Get-Mailbox -Arbitration -Filter {name -eq $name} -IgnoreDefaultScope -ResultSize 1 );
if ($mbxs.Length -eq 0)
Write-ExchangeSetupLog -Info (“Retrieving mailbox databases on Server=$RoleFqdnOrName.”);
$dbs = @(Get-MailboxDatabase -Server:$RoleFqdnOrName -DomainController $RoleDomainController);
if ($dbs.Length -ne 0)
Write-ExchangeSetupLog -Info (“Retrieving users with Name=$name.”);
$arbUsers = @(Get-User -Filter {name -eq $name} -IgnoreDefaultScope -ResultSize 1);
if ($arbUsers.Length -ne 0)
Write-ExchangeSetupLog -Info (“Enabling mailbox $name.”);
$sysMbx = Enable-Mailbox -Arbitration -Identity $arbUsers[0] -DisplayName $dispName -database $dbs[0].Identity;
if ($mbxs[0].DisplayName -ne $dispName )
Write-ExchangeSetupLog -Info (“Setting DisplayName=$dispName.”);
Set-Mailbox -Arbitration -Identity $mbxs[0] -DisplayName $dispName -Force;
$sysMbx = $mbxs[0];

# Set the Organization Capabilities needed for this mailbox
if ($sysMbx -ne $null)
# We need 1 GB for uploading large OAB files to the organization mailbox
Write-ExchangeSetupLog -Info (“Setting mailbox properties.”);
set-mailbox -Arbitration -identity $sysMbx -UMGrammar:$true -OABGen:$true -GMGen:$true -ClientExtensions:$true -MailRouting:$true -MessageTracking:$true -PstProvider:$true -MaxSendSize 1GB -Force;
Write-ExchangeSetupLog -Info (“Cannot find arbitration mailbox with name=$name.”);
Write-ExchangeSetupLog -Info “Skipping creating E15 System Mailbox because of insufficient permission.”
” was run: “Database is mandatory on UserMailbox.”.

The reason that I was receiving this particular error was because I had a previous installation of Exchange on this server and the arbitration mailboxes had become corrupted for obvious reasons (hard disk failure).   The quickest way to fix up this issue is to remove the AD accounts associated with the now broken arbitration mailboxes, and then re-run /preparead which would recreate all the required AD accounts.

This put me in somewhat of a conundrum because I had already updated the schema to support an Exchange 2016 install and as the arbitration mailboxes had been created in 2010 I couldn’t run /preparead using the 2010 setup files as the schema wouldn’t support it.  So what was I going to do…  I had to determine which of the arbitration / system mailboxes had been created as part of the 2016 /preparead as I suspected that it was these mailboxes that were causing me the grief.

To view the arbitration mailboxes I ran this command:

Set-ADServerSettings -ViewEntireForest $true

Get-mailbox -Arbitration | fl name,Database,DisplayName,ServerName

This command output a list of all of the arbitration mailboxes in the entire AD forest.  The reason for running this command is because the arbitration or system mailboxes do not appear in the Exchange Admin Centre.  Have a look at this blog post by Tony Redmond which has a really good explanation of what the arbitration mailboxes are and why they are so important.

The results that I got from the command looked a little like the below:


Except that one of my arbitration mailboxes was complaining about corruption.


What I had to do, was remove the associated user account from Active Directory.  These accounts are typically created.  Once I had removed the user accounts for the corrupted arbitration mailboxes I was able to run the Exchange 2016 setup again and this time it completed without any errors!



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