EAC, can't find system mailbox

Question

Please assist me as I am not able to export mailbox as .pst file on each, says system mailbox couldn't be found yet when i run the exchange management shell to check attributions and other stuff, everything is there.

Answer 1

Hi Qh

Thank you for reaching out to Microsoft Q&A

As far as I know, this error occurs because on‑premises Exchange PST export uses the Mailbox Replication Service (MRS) and depends on Exchange system/arbitration mailbox objects in Active Directory. When the export process can’t locate the required SystemMailbox object, the request fails, even if the user mailbox attributes look correct.

You can follow the below instructions to see if it can help you:

The New-MailboxExportRequest cmdlet requires the mailbox to be on an Exchange server, not on a DAG node that's in maintenance mode or a server where the mailbox database is dismounted.

Run this first to verify the mailbox database that hosts the mailbox is mounted

Get-MailboxDatabase -Status | Select Name, Mounted, Server

Next one, run this:

$mbx = Get-Mailbox "******@domain.com" $mbx | Select DisplayName, ExchangeGuid, Alias, Database 
Get-ADUser -Identity $mbx.SamAccountName -Properties msExchMailboxGuid | Select msExchMailboxGuid 

If ExchangeGuid from Exchange and msExchMailboxGuid from AD don't match → that's your problem.

In this case, you can fix it by:

Set-Mailbox "******@domain.com" -ExchangeGuid <GUID-from-AD>

Next step, check if missing Mailbox Import Export RBAC Role

# Check if the role is assigned
Get-ManagementRoleAssignment -Role "Mailbox Import Export" -GetEffectiveUsers
# Assign it if missing (replace with your admin group)
New-ManagementRoleAssignment -Role "Mailbox Import Export" -User "AdminUser"

Note: After assigning this role, you must close and reopen EMS for it to take effect.

Technically, the New-MailboxExportRequest cmdlet cannot write to a local drive. The destination must be a UNC network path, and the Exchange Trusted Subsystem must have write permissions on that share.

New-MailboxExportRequest -Mailbox "******@domain.com" -FilePath "\\Server\ShareName\user.pst" 

To grant the necessary permissions to the share:

Grant-SmbShareAccess -Name "ShareName" -AccountName "Exchange Trusted Subsystem" -AccessRight Full

Finally, review export request status for detailed error information

Get-MailboxExportRequest | Get-MailboxExportRequestStatistics | Select DisplayName, Status, FailureCode, Message

Hope my answer will help you.

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Answer 2

To export a mailbox to a .pst file in Exchange, the following conditions must be met and verified, especially when the EAC reports that a system mailbox or object cannot be found:

1. Verify the Mailbox Import Export role The Mailbox Import Export role is required and is not assigned to any role group by default.

• Add the Mailbox Import Export role to a role group that the admin account belongs to.
• Log off and log on again after changing permissions so they take effect.

Without this role, export options in EAC and related operations can fail or be unavailable.

2. Verify the UNC share and permissions Mailbox export to .pst requires a UNC network share and correct permissions:

• Use a UNC path like \\Server\Share\Export.pst or \\LocalServerName\c$\Export.pst when specifying the target file.
• Ensure the Exchange Trusted Subsystem security group has Read/Write permissions on that share. If this permission is missing, export attempts will fail with errors when using EAC or Shell.

3. Use EAC correctly to export mailbox In the EAC, the export is initiated from the user mailbox, not from a system mailbox:
4. Go to Recipients > Mailboxes.
5. Select the user mailbox.
6. Click More options (ellipsis icon) and choose Export to a PST file.
7. In the wizard, choose whether to export the primary mailbox or archive.
8. Specify the UNC path for the .pst file.
9. Optionally configure notification email recipients and finish the wizard.

If EAC reports that a system mailbox cannot be found while everything looks correct in Shell, still verify that:

• The Discovery/system mailboxes required for eDiscovery or metadata are present and healthy.
• No required system mailbox has been deleted or moved improperly.

4. Validate export requests and status in Shell After starting an export (from EAC or Shell), use these commands to validate that the export request exists and to check status:

Get-MailboxExportRequest

To check a specific mailbox:

Get-MailboxExportRequest -Mailbox "<MailboxIdentity>" | Format-List Name,FilePath,Mailbox,Status

For detailed statistics:

Get-MailboxExportRequestStatistics -Identity "<MailboxIdentity>\<MailboxExportRequestName>" | Format-List

If EAC cannot find the target object but Shell can, and the environment has multiple domains, also consider specifying a domain controller explicitly when creating the export request in Shell using -DomainController (example pattern from the context):

New-MailboxExportRequest -Mailbox "User One" -FilePath \\server\share\export.pst -DomainController DC1.child.domain.corp

This addresses cases where directory lookups are scoped to the local domain and the mailbox or target user is in a child domain.

5. System mailbox considerations If the issue is actually with a Discovery/system mailbox (for example, used by eDiscovery) being missing or corrupted, it must be re-created so dependent features work correctly. For Exchange 2013, this is done by re-running Setup with /preparead from the installation media directory to re-create the Discovery system mailbox.

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References:

• Mailbox imports and exports in Exchange Server
• Procedures for mailbox exports to .pst files in Exchange Server
• Can't use EAC to export to a PST file when the target user belongs to a child domain in Exchange Server 2013
• Re-create the Discovery system mailbox
• In-Place eDiscovery in Exchange 2013