Unable to access an account or mailbox: For Exchange users, this error means that the mailbox could not be accessed. For Microsoft 365 users, this error indicates that Microsoft 365 is confused about which mailbox it should connect to. This may happen if you deleted and recreated an account, as Microsoft 365 will find two accounts (one active and one deleted).
Refer to the instructions below for your software.
- Check the admin account:
- Make sure it is fully qualified (don't use administrator - use domain\administrator or firstname.lastname@example.org.
- Make sure it has a mailbox you can log into (use OWA).
- Make sure it can open the end user's mailbox.
- Make sure the email address is correct.
- Make sure the mailbox can be logged in to.
- Log in to your account at http://portal.microsoftonline.com.
- Click on the Users and Groups tab on the left.
- Click on the Deleted users at the top.
- Delete the offending user(s).
You can also use PowerShell to check for deleted users that conflict with active ones:
- Go to Windows start, search for Windows PowerShell (PowerShell should already be installed on your computer).
- Start PowerShell under an administrator context (right-click "run as administrator").
- Run the following PowerShell commands (one at a time):
$LiveCred = Get-Credential
Install-Module -Name ExchangeOnlineManagement
Import-Module -Name ExchangeOnlineManagement
Connect-ExchangeOnline -ConnectionUri https://ps.outlook.com/powershell/ -Credential $LiveCred
For the last command, try with the email address of both the end user mailbox, and the admin account (if applicable). If you see more than one result, then Microsoft 365 is confused about which mailbox to connect to. Either create a new account or open a ticket with Microsoft 365 Support to have the deleted entry purged.
Note: Mailboxes cannot be completely removed if litigation hold has been placed on them. You will need to remove the litigation hold first from the inactive mailboxes before they can be deleted.