Unable to access an account or mailbox

Error

Unable to access an account or mailbox.

Cause

• 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 delete and recreate an account, as Microsoft 365 will find two accounts (one active and one deleted).

Resolution

Refer to the instructions below for your software.

Exchange Server

1. Check the admin account:
   • Make sure it is fully qualified (don't use administrator - use domain\administrator or administrator@domain.com.
   • Make sure it has a mailbox you can log into (use OWA).
   • Make sure it can open the end user's mailbox.
2. Check the user account
   • Make sure the email address is correct.
   • Make sure the mailbox can be logged in to.

Microsoft 365

1. Log in to your account at http://portal.microsoftonline.com.
2. Click on the Users and Groups tab on the left.
3. Click on the Deleted users at the top.
4. Delete the offending user(s).

You can also use PowerShell to check for deleted users that conflict with active ones:

1. Go to Windows Start.
2. Search for Windows PowerShell (PowerShell should already be installed on your computer).
3. Start PowerShell under an administrator context (right-click "run as administrator").
4. Run the following PowerShell commands (one at a time):

   Set-ExecutionPolicy Unrestricted
$LiveCred = Get-Credential
Install-Module -Name ExchangeOnlineManagement
Import-Module -Name ExchangeOnlineManagement
Connect-ExchangeOnline -ConnectionUri https://ps.outlook.com/powershell/ -Credential $LiveCred
Get-User myuser@domain.com

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.