New migration from on premise Exchange 2016 to Office 365. Expert in Exchange, new to Office 365.

Users went fine and are using the system without problem.

Public folders not only failed, but disappeared from on premises and didn't show I Office 365. After many hours troubleshooting with Microsoft, I decided to delete all Public Folder and manually recreate them in Office 365. Since they disappeared ECP was of no help so I deleted them using ADSI Edit. After everything sync'ed, verified that they are gone on premise.

Now when I try to create them in Office 365, it says that the email address exists. It doesn't in on premise, but I can see them in Outlook -> People online. Can't send or receive mail using those addresses and I need to delete them so I can recreate them correctly. They are critical to our operation.

  • Have you got an Active Directory available in your portal and can delete there?
    – LTPCGO
    Commented Jan 7, 2020 at 3:32

1 Answer 1


Make sure there aren't any existing public folders or public folder mailboxes in Exchange Online. Get-Mailbox -PublicFolder Then check which mailbox using this email address by get-mailbox| where {$_.EmailAddresses -match "user name"} | ft Name, RecipientType, EmailAddresses and change it.

Or you could check the sync status in AAD connect, find the source object (on-premise) and delete it in Exchange 2016.

Troubleshoot an object that is not synchronizing with Azure Active Directory https://docs.microsoft.com/en-us/azure/active-directory/hybrid/tshoot-connect-object-not-syncing>

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