Token type 'PFAT' is not supported for MSA scenario 'PFAT'

[A9G-Data-Droid]

Describe the bug

I am seeing an intermittent error that started today:

Token type 'PFAT' is not supported for MSA scenario 'PFAT'

Out of 10 emails, two have failed with this error. So while I think it's server side there is also nothing on the internet about this error. Seems like I'm the first person to see or report it. So if there is any insight about what this error means, it would like to get it documented.

Expected behavior

My code has been sending many emails per day flawlessly for over a year.

How to reproduce

/// <summary>
/// Send email using the credentials and send from used in constructor.
/// </summary>
/// <param name="theEmail">A complete email message, use EmailTemplate to generate.</param>
/// <param name="cancelToken">To stop the request.</param>
[PublicAPI]
public async Task SendMailAsync(Message theEmail, CancellationToken cancelToken = new())
{
    // Define our new Microsoft Graph client. Use the credentials we specified above.
    using GraphServiceClient graphServiceClient = new GraphServiceClient(_existingCredentials, _scopes, _endpoint);

    var requestBody = new SendMailPostRequestBody
    {
        Message = theEmail,
        SaveToSentItems = true,
    };

    // Send mail as the given user. 
    var fromUser = graphServiceClient.Users[_sendAsUserID];
    await fromUser.SendMail.PostAsync(requestBody, null, cancelToken).ConfigureAwait(false);
}

SDK Version

5.56.0

Latest version known to work for scenario above?

5.56.0

Known Workarounds

If you send it again, it goes through. Likely a server issue?

Debug output

Click to expand log

```

{
"error": {
"code": "TokenTypeNotSupported",
"message": "Token type 'PFAT' is not supported for MSA scenario 'PFAT'",
"innerError": {
"oAuthEventOperationId": "-REDACTED-",
"oAuthEventcV": "PTLBqqwT525Pt4yTB0VD0Q.1",
"errorUrl": "https://aka.ms/autherrors#error-InvalidMsaTicket",
"requestId": "-REDACTED-",
"date": "2024-08-15T17:17:26"
}
}
}

</details>


### Configuration

- OS: Windows 10 x64

### Other information

I believe the issue is server side. Looking to confirm. 

Also, what's a PFAT?

[andrueastman]

Thanks for raising this @A9G-Data-Droid

Any chance you can post the same question at https://aka.ms/askGraph to get feedback from the API owners on whther this is expected? As this repo is mainly intended for sdk related issues, we may not be best placed to answer or give feedback on API related issues.

[A9G-Data-Droid]

I got the following response:

Our engineering team has found a change they believe had caused this issue. They're reverted the change and are seeing improvement. If you could please help us confirm the issues are since resolved? For reference, you should see communications posted under EX862948 in your Service Health Dashboard.

This confirms it is not an SDK issue. If you receive this error, there is nothing wrong with your code. It is server side.