We are currently running Exchange 2016 on premises with modern public folders. We are migrating to Exchange Online using a full hybrid configuration since the migration will take a few weeks. I am trying to set up Exchange Online so that people whos mailboxes have been migrated can access the public folders on our local Exchange 2016 server. I am using this as my procedure https://docs.microsoft.com/en-us/exchange/collaboration-exo/public-folders/set-up-modern-hybrid-public-folders. We have our active directory synced with Office 365 using Azure AD Connect. Most of the public folders are mail-enabled.

When I run the second step in the referenced article (Set-OrganizationConfig -PublicFoldersEnabled Remote -RemotePublicFolderMailboxes PublicFolderMailbox1,PublicFolderMailbox2,PublicFolderMailbox3) in the Exchange Online PowerShell window, I get the message

Couldn't find object "PublicFolderMailbox1". Please make sure that it was spelled correctly or specify a different object.

The Sync-MailPublicFolders.ps1 was run over 24 hours ago and there were no sync errors reported from AADConnect. Where can I look to see why the objects didn't sync? Or is there a better document/procedure I should be following?

Thank you.


There was an AADConnect synchronization rule to not sync disabled users. Since the Public Folder Mailbox users are disabled they were not being synced. We removed the rule and now all is well.

Thanks for the help.

  • Are all the system PFs synced to Exchange Online now? – Jayce Yang Jun 20 at 5:39
  • They appear to be. – Eric Logsdon Jun 21 at 11:11

You could check if the pubic folders are synced in EAC of Exchange Online. If not, please check the CsvSummaryFile, it is the path to where you would like to log synchronization operations and errors, in .csv format.

Or re-run Sync-MailPublicFolders.ps1 -Credential (Get-Credential) -CsvSummaryFile:sync_summary.csv with the -WhatIf parameter.

  • In the csv file, 69 folders were successful, 6 had invalid aliases. They appear to be old folders dragged from upgrade to upgrade (OAB Version 2, Schedule+FreeBusyInformation-Atlanta, etc.). I can't locate them in EAC on prem or via powershell. – Eric Logsdon Jun 12 at 15:20
  • You could make sure if they are the system public folders. If yes, you could mail-disable them, then re-run the sync scripts. – Jayce Yang Jun 13 at 2:35
  • If I can't see them in the EAC or locate them via PowerShell, I'm not sure how to mail-disable them. – Eric Logsdon Jun 13 at 18:19
  • Could you ignore these folders in your cmdlet? – Jayce Yang Jun 17 at 3:12

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