Error: ErrorNonExistentMailbox

Description

ErrorNonExistentMailbox = Mailbox No Longer Exists

This error occurs when the Exchange server responds with:
“No mailbox with such GUID.”

It indicates that the mailbox associated with the current grant no longer exists or is not accessible on the Exchange server.

Possible Causes

• The mailbox was deleted
• The mailbox was migrated to another server or environment
• The mailbox is temporarily unavailable
• There are server-side issues affecting mailbox access

Resolution Steps

1. Contact Your Exchange Administrator

Ask your Exchange administrator to verify the mailbox status:

• Has the mailbox been deleted, migrated, or temporarily disabled?
• Is the mailbox still accessible or restored at a different location?
• Are there any server-side issues impacting mailbox availability?

2. If the Mailbox Can Be Restored at the Same Location

• Re-authenticate the existing grant after confirmation from the Exchange administrator
• This will:
  • Preserve the existing grant ID
  • Maintain current configuration

3. If the Mailbox Was Permanently Deleted or Migrated

• Delete the existing grant
• Create a new grant

This allows Exchange Autodiscovery to:

• Locate the correct mailbox
• Connect to the appropriate server endpoint

Additional Support

If the issue persists after completing the steps above, please contact the support team for further investigation and assistance.

Updated April 21, 2026 21:09