Outlook default error

Windows 11 fully updated on new PC. Outlook New desktop version, updated. 1 Email account inside, works well, password confirmed in Outlook New, and on email account website, no account issue.
During Windows startup, and during Outlook New startup, "Default Email" error. Outlook does not know it is the default email client. Settings > Apps > Default > Outlook New, made it the default in all of about 20 categories. Outlook Classic is on Windows, but has never been opened.
Reinstalled O365, which includes Outlook New, restarted PC many times. No viruses.
No other email addresses in Outlook New, or in significant use elsewhere.
Windows is signed in with a personal MS account, and O365, Outlook New, Onedrive, Edge, are signed in with a different, Work MS Account.
No other errors anywhere in Windows.
How to solve this error? No Ai replies please. Thank you.

-- "Default Email" error. Outlook does not know it is the default email
Is this a "Do you want to make Outlook your default email" type of option message? Or a hard error message that prevents Outlook from starting? What's the exact working of the message or a screen shot?

Long Shot - Do you have a UseNewOutlook value under HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Preferences ?
Identifying and Switching Between New and Classic Outlook Interfaces

Thank you horn, the error comes up everytime the app is started, it is not asking me to choose a default app, it is displaying an system error. I appreciate the Registry suggestion, but I do not use the registry anymore, I used to edit the registry, but the last time I did that, it bluescreened the PC permanently, luckily it was an empty PC that I was practicing on, so there was no loss.

Under Default apps there should be about 6 entries for Outlook (formally known as New Outlook). The name New Outlook has been dropped to Outlook about a month or two back.

Suspect that has resulted in much confusion with Desktop/O365/Classic Outlook.

As I only have Outlook (formally known as New Outlook) installed and no version of MS Office.
Used daily with 6 Email Accounts, No errors.

A simplistic view would be to uninstall one of those "Outlook" mail clients.

The reference in post #2 adds to the confusion as the "New" in the name and Icon is no longer there...

2Savage said:

Thank you horn, the error comes up everytime the app is started, it is not asking me to choose a default app, it is displaying an system error. I appreciate the Registry suggestion, but I do not use the registry anymore, I used to edit the registry, but the last time I did that, it bluescreened the PC permanently, luckily it was an empty PC that I was practicing on, so there was no loss.

Click to expand...

Every switch you flick or app configuration you make will alter the registry, sometime it's quicker to address things directly.