DefaultPublicFolderMailbox emtpy and EffectivePublicFolderMailbox pointing to old name POST migration

dirkdigs 921 Reputation points

i have migrated public folders from 2019 to exchange online
we had co-existence set for hybrid.
now that my PF's have been moved to ExO how to do update the DefaultPublicFolderMailbox and/or EffectivePublicFolderMailbox attribs for ALL users?

i have done this for single user and tested works good

Set-Mailbox -Identity test123 -DefaultPublicFolderMailbox PFMailbox1

but im looking for cmdlt to update ll users

Also should the EffectivePublicFolderMailboxmailbox value not update on its own automatically as long as IsExcludedFromServingHierarchy value is set to $false?
Maybe because we have been running hybrid for some time and it was hard coded at some point ?

Microsoft Exchange Online Management
Microsoft Exchange Online Management
Microsoft Exchange Online: A Microsoft email and calendaring hosted service.Management: The act or process of organizing, handling, directing or controlling something.
4,167 questions
Microsoft Exchange Hybrid Management
Microsoft Exchange Hybrid Management
Microsoft Exchange: Microsoft messaging and collaboration software.Hybrid Management: Organizing, handling, directing or controlling hybrid deployments.
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Accepted answer
  1. Joyce Shen - MSFT 16,641 Reputation points

    Hi @dirkdigs

    DefaultPublicFolderMailbox is technically used for modern public folder access in Exchange Online. It can be set per user mailbox to tell Autodiscover which SMTP address to return in the PublicFolderInformation section of the XML response. EffectivePublicFolderMailbox is a property that cannot be set, but it is populated with one of the remote public folder proxy mailboxes that is set in the Organization Config, and as stated previously, it is completely random. The Microsoft article mentions nothing about this, but I found that you can force Exchange Online to return a mailbox of your choosing by setting the DefaultPublicFolderMailbox attribute. Changing the DefaultPublicFolderMailbox property changes the EffectivePublicFolderMailbox property as well.

    And the command you shared above can be used to set the DefaultPublicFolderMailbox attribute for a mailbox
    Set-Mailbox -Identity test123 -DefaultPublicFolderMailbox PFMailbox1
    And according to the introduction of the parameter: -IsExcludedFromServingHierarchy, However, if an administrator has set the DefaultPublicFolderMailbox property on a user mailbox to a specific public folder mailbox, the user will still access the specified public folder mailbox even if the IsExcludedFromServingHierarchy parameter is set for that public folder mailbox.

    And If you want to update the command for all users, you could use the command below to meet this need:

    Get-Mailbox | Set-Mailbox -DefaultPublicFolderMailbox PFMailbox1  

    Below links for your reference as well:
    Legacy Public Folder Coexistence in Multi-Site Hybrid Deployments

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