Nota: Este artigo foi publicado originalmente em 2013. Alguns passos, comandos ou versões de software podem ter mudado. Consulte a documentação atual de Exchange 2010 para as informações mais recentes.

Introdução

If you have ever tried to decommission an Exchange 2010 server, you may have encountered an error telling you that arbitration mailboxes still reside on that server’s database. These hidden system mailboxes are not visible in the Exchange Management Console (EMC) by default, which causes confusion for many administrators. This article explains what arbitration mailboxes are, why they exist, how to manage them, and how to move them safely during server migrations.

What Are Arbitration Mailboxes?

Arbitration mailboxes are special system mailboxes created automatically during Exchange 2010 installation. They are used internally by Exchange to manage approval workflows and other system-level operations. Unlike regular user mailboxes, arbitration mailboxes do not belong to any user and are hidden from the Global Address List (GAL).

Microsoft defines them as follows:

Arbitration mailboxes are used for managing approval workflow. For example, an arbitration mailbox is used for handling moderated recipients and distribution group membership approval.

Functions Performed by Arbitration Mailboxes

Exchange 2010 typically creates two arbitration mailboxes during installation, each serving specific purposes:

1. SystemMailbox{1f05a927-xxxx-xxxx-xxxx-xxxxxxxxxxxx}

This mailbox handles:

  • Moderated Transport: When a message is sent to a moderated recipient (mailbox, distribution group, or mail contact), it is held in this arbitration mailbox until a moderator approves or rejects it.
  • Distribution Group Membership Approval: When a user requests to join a distribution group that requires owner approval, the request is stored and managed here.

2. FederatedEmail.4c1f4d8b-8179-4148-93bf-00a95fa1e042

This mailbox handles:

  • Federated sharing and delegation tokens used for cross-organization calendar and free/busy sharing.
  • Organization-wide system messages.

Additional Arbitration Mailboxes (Post-SP1)

After applying Exchange 2010 Service Pack 1 or later, you may see an additional arbitration mailbox:

  • SystemMailbox{e0dc1c29-89c3-4034-b678-e6c29d823ed9}: Used for Offline Address Book (OAB) generation and distribution in Exchange 2010 SP1 and later.

How to View Arbitration Mailboxes

Since arbitration mailboxes are hidden from the EMC, you must use the Exchange Management Shell (EMS) to view them.

List All Arbitration Mailboxes

Get-Mailbox -Arbitration

View Detailed Information

Get-Mailbox -Arbitration | Format-List Name, DisplayName, Database, ServerName

Example Output

Name        : SystemMailbox{1f05a927-89c0-4725-adca-4527114196a1}
DisplayName : Microsoft Exchange Approval Assistant
Database    : Mailbox Database 0628741285
ServerName  : EXCH01

Name        : FederatedEmail.4c1f4d8b-8179-4148-93bf-00a95fa1e042
DisplayName : Microsoft Exchange
Database    : Mailbox Database 0628741285
ServerName  : EXCH01

How to Move Arbitration Mailboxes

When migrating to a new Exchange server or decommissioning an old one, you must move all arbitration mailboxes to a database on the new server before you can uninstall Exchange from the old server.

Move All Arbitration Mailboxes to a New Database

Get-Mailbox -Arbitration | New-MoveRequest -TargetDatabase "NewServerDB"

Monitor the Move Requests

Get-MoveRequest -MoveStatus Queued
Get-MoveRequest | Get-MoveRequestStatistics

Verify Completion

Get-Mailbox -Arbitration | Format-List Name, Database

Confirm that all arbitration mailboxes now show the new target database.

Clean Up Completed Move Requests

Get-MoveRequest -MoveStatus Completed | Remove-MoveRequest

Why You Must Never Delete Arbitration Mailboxes

Deleting arbitration mailboxes will break the following Exchange functionality:

  • Moderated Transport will stop working entirely. Messages sent to moderated recipients will be silently dropped or generate NDRs.
  • Distribution group join/leave approvals will fail.
  • OAB generation will fail if the OAB arbitration mailbox is removed (Exchange 2010 SP1+).
  • Federation and cross-organization sharing will break without the federated email mailbox.

If you accidentally delete an arbitration mailbox, you may need to recreate it using the Exchange setup process with the /PrepareAD switch:

Setup.com /PrepareAD

The Moderated Transport Feature

The Moderated Transport feature in Exchange 2010 allows administrators to require approval for messages sent to specific recipients. The workflow operates as follows:

  1. A user sends a message to a moderated recipient.
  2. The Hub Transport server intercepts the message and stores it in the arbitration mailbox.
  3. An approval request is sent to the designated moderator(s).
  4. The moderator approves or rejects the message through Outlook or OWA.
  5. If approved, the message is released from the arbitration mailbox and delivered to the recipient. If rejected, the sender receives an NDR.

You can configure moderated transport on any recipient type:

# Enable moderation on a distribution group
Set-DistributionGroup "All Employees" -ModerationEnabled $true -ModeratedBy "admin@domain.com"

# Enable moderation on a mailbox
Set-Mailbox "CEO" -ModerationEnabled $true -ModeratedBy "executive.assistant@domain.com"

Solução de Problemas Tips

  • Cannot uninstall Exchange: Run Get-Mailbox -Arbitration | Format-List Database to check if any arbitration mailboxes still reside on the server you are trying to remove.
  • Moderation not working: Verify the arbitration mailbox exists and is healthy with Test-MAPIConnectivity -Identity "SystemMailbox{1f05a927-*}".
  • OAB not generating: Ensure the OAB arbitration mailbox (SystemMailbox{e0dc1c29-...}) exists and the mailbox database is mounted.
  • Move request stuck: Check move request status with Get-MoveRequest | Get-MoveRequestStatistics and look for errors in the detailed status.

Resumo

Arbitration mailboxes are critical system mailboxes in Exchange 2010 that support moderated transport, distribution group approval workflows, OAB generation, and federated sharing. They are hidden from the Exchange Management Console and can only be managed through the Exchange Management Shell. When decommissioning or migrating Exchange servers, always move arbitration mailboxes to the new database before uninstalling Exchange. Never delete them, as doing so will break essential Exchange functionality.

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