Unexpected PublicFolderMailBoxes dynamic distribution groups in Exchange Server 2016

Original KB number:   4035952


Consider the following scenario:

  • You have an Active Directory site that has more than one domain controller.
  • The Exchange Server 2016 server in the site has Cumulative Update 6 installed.
  • The first public folder mailbox is created on Exchange Server 2016.

In this scenario, multiple dynamic distribution groups are created unexpectedly. The names of these dynamic distribution groups begin with PublicFolderMailboxes.

Screenshot of unexpected PublicFolderMailBoxes dynamic distribution groups


Exchange Server 2016 creates a dynamic distribution group for hierarchy sync of public folders. In an environment that has multiple domain controllers, the entry for the dynamic distribution group is created in one of the domain controllers. Immediately, a process looks up the dynamic distribution group from a different domain controller to verify whether the dynamic distribution group exists. Because Active Directory replication hasn't happened yet, the dynamic distribution group is not replicated. Therefore, it is not found and is created again. Until replication occurs, a new dynamic distribution group is created each time that the process runs.


To work around this issue, hard code a domain controller on the Exchange Server that hosts the primary hierarchy public folder mailbox so that the Exchange Server only communicates to the domain controller. To do this, follow these steps:

  1. Remove the unexpected dynamic distribution groups by running the following command in the Exchange Management Shell:

    Get-DynamicDistributionGroup -IncludeSystemObjects PublicFolderMailboxes* | Remove- DynamicDistributionGroup
  2. In the Application log in Event Viewer, filter the log to show Event ID 2080.

  3. Locate the latest Event ID 2080. In the description, you should find more than one domain controller listed under In-site.


    DC01.domain.com CDG 1 7 7 1 0 1 1 7 1
    DC02.domain.com CDG 1 7 7 1 0 1 1 7 1
  4. Copy the FQDN of a listed domain controller that is also a global catalog server.

  5. Run the following command in the Exchange Management Shell:

    Set-ExchangeServer -Identity <name of Exchange server> -StaticDomainControllers <FQDN of DC> -StaticConfigDomainController <FQDN of DC> -StaticGlobalCatalogs <FQDN of DC>


    Set-ExchangeServer -Identity e161 -StaticDomainControllers DC01.domain.com  -StaticConfigDomainController DC01.domain.com  -StaticGlobalCatalogs DC01.domain.com
  6. Wait 15 minutes or a little longer for Exchange topology discovery to happen. This is when the next Event ID 2080 is logged. In the description of the Event ID 2080, you should see only one domain controller listed under In-site.

  7. Run the following command in the Exchange Management Shell:

    Get-Mailbox -PublicFolder | ?{$_.IsRootPublicFolderMailbox -eq "true"} | Update-PublicFolderMailbox
  8. You should see only one dynamic distribution group created. Wait for 15 or 20 minutes, and then run the following command to verify whether a single dynamic distribution group was created:

    Get-DynamicDistributionGroup -IncludeSystemObjects PublicFolderMailboxes*
  9. Remove the hard coding of the domain controller by running the following command:

    Set-ExchangeServer -Identity <name of Exchange server> -StaticDomainControllers $null -StaticConfigDomainController $null -StaticGlobalCatalogs $null


Microsoft is investigating the problem and will update as more information becomes available.