Hello James,
Thank you for posting to Microsoft Q&A forum. I completely understand how stressful it can be to lose track of an old email username, especially when the app you used to rely on has fundamentally changed.
Please note that the old Windows Mail app was officially retired at the end of 2024 and fully replaced by the new Outlook for Windows. Because the service is discontinued, the old experience is no longer supported.
However, your emails are not lost. The old Mail app acted only as a viewer for emails that are safely stored on your email provider's servers. To access your old emails, you will need to recover your forgotten username directly through your provider:
- For Microsoft Accounts (@outlook.com, @hotmail.com, @live.com): Visit the Microsoft Username Recovery page (https://account.live.com/username/recover) and enter any alternate email address or phone number you may have linked to the account.
- For Third-Party Accounts (Gmail, Yahoo, etc.): You will need to use the specific "Forgot Username" or account recovery tools provided by those services.
I hope this clarifies the situation and helps point you in the right direction to recover your account details. Please feel free to reply if you need any further assistance!
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