Sending, receiving, and organizing email in Outlook.com
This looks more like Outlook has lost or removed the account connection than the mailbox actually being emptied. The “Add or create account” screen is consistent with Outlook having no account currently configured. Microsoft’s guidance is to add the account again using the same email address.
If the account uses IMAP, Microsoft specifically notes that removing/re-adding it does not delete the server-stored messages.
Try:
- Select Add account.
- Enter the same email address you previously used.
- Sign in and allow Outlook to synchronize.
- If the account cannot be added or the messages still don't appear, use Microsoft's Outlook send/receive diagnostic tool on the affected PC.
So I would not start trying to recover deleted emails yet. First restore the account connection.