Attempting to delete an Exchange Server 2016 mailbox database previously used to migrate public folders from Exchange 2010 throws the error: “This mailbox database is associated with one or more active PublicFolderMailboxMigration requests…”

I recently had to assist a client with migrating their Exchange Server 2010 public folders to Exchange Server 2016 and ran into a situation where the mailbox database storing the public folder mailboxes would throw the following error message when I attempt to delete it via the GUI or PowerShell:

This mailbox database is associated with one or more active PublicFolderMailboxMigration requests. To get a list of
all PublicFolderMailboxMigration requests associated with this database, run Get-PublicFolderMailboxMigrationRequest |
?{ $_.RequestQueue -eq "<Database ID>" }. To remove a PublicFolderMailboxMigration request, run
Remove-PublicFolderMailboxMigrationRequest <Recipient ID\Request Name>.
    + CategoryInfo          : InvalidOperation: (empfdb01:DatabaseIdParameter) [Remove-MailboxDatabase], AssociatedMRS
   RequestExistsException
    + FullyQualifiedErrorId : [Server=BMEXMB01,RequestId=65decc2b-2925-48cf-91d0-aba27ab1329f,TimeStamp=1/30/2017 1
   :20:19 PM] [FailureCategory=Cmdlet-AssociatedMRSRequestExistsException] A32E1F9E,Microsoft.Exchange.Management.Sys
  temConfigurationTasks.RemoveMailboxDatabase
    + PSComputerName        : bmexmb01.contoso.com

After ensuring that there were no Public Folder Mailbox Migration requests by executing the Get-PublicFolderMailboxMigrationRequest cmdlet, I did a quick search on the internet and found the following post:

https://social.technet.microsoft.com/Forums/office/en-US/54fd0db4-11d3-421c-92e8-d4050338a907/trouble-removing-2016-mailbox-database?forum=Exch2016Adm

… where a person indicated that there may be a lingering object in the Configuration container that is not returned by the PowerShell cmdlets.  I then went ahead and launched ADSIedit, connected to the Configuration container then browsed to:

Configuration > Services > Microsoft Exchange > ExchOrganization > Mailbox Replication displayed the following:

The node that appeared to be out of place was the one named:

CN=PublicFolderMailboxMigrationRequestsCNF:11714980-d0a3…

Browsing into that node displayed the following items:

Opening these items showed that they were objects that corresponded to the day I had started the migration batch for the public folder migration so I went ahead and deleted these items in the folder then forced replication via repadmin /syncall /AdeP on a domain controller and was then able to delete the mailbox database.