Outlook issues when the msExchMasterAccountSID attribute exists on a user account in Active Directory

Original KB number:  2996202


After a mailbox move or migration, one or more of the following issues may be displayed:

  • Some mailboxes show as linked or shared rather than as user mailboxes.

  • Repeated mailbox credential prompts in Microsoft Outlook or Outlook Web App (OWA)

  • Unexpected delays in, or halted mail flow.

  • Problems accessing Public Folders, and sometimes resulting in the following error:

    Cannot expand the folder. Microsoft Exchange is not available. Either there are network problems or the Exchange Server is down for maintenance.


This behavior can occur if a regular user account has the msExchMasterAccountSID attribute populated in Active Directory.


To correct this issue, run the following PowerShell command from the Exchange Management Shell:

Set-User -Identity useraddress -LinkedMasterAccount $null

For example:

Set-User -Identity user@fabricam.com -LinkedMasterAccount $null

This command will remove the msExchMasterAccountSID attribute from the user's account.

More information

The msExchMasterAccountSID attribute shouldn't exist for a regular user account in Active Directory. A regular user will be identified as having an msExchRecipientTypeDetails attribute value of 1 (1 = normal mailbox, 2 = linked mailbox.)

If msExchRecipientTypeDetails = 1, then msExchMasterAccountSID shouldn't exist on the account in Active Directory.

For more information on possible values for the msExchRecipientTypeDetails attribute, see the following Office 365 blog post:

O365: Exchange and AD - How msExchRecipientDisplayType and msExchangeRecipientTypeDetails Relate to Your On-Premises