Official Windows App SDK PFN mapping email rejects request with SMTP 550 5.4.1

I am following the official Windows App SDK push notifications quickstart to map a packaged Win32 app's Package Family Name (PFN) to its Microsoft Entra AppId.

The documentation instructs developers to email Win_App_SDK_Push@microsoft.com with the PFN, AppId, and ObjectId. The message was rejected by Microsoft's mail server:

550 5.4.1 Recipient address rejected: Access denied.

For privacy and least exposure, the complete mapping identifiers have been omitted from this public post:

• PFN: com.nos2studios.nos2_[redacted]
• AppId: 66bc9d01-…-0f8b
• ObjectId: 5f1b5c29-…-5561

I can provide the complete PFN, AppId, and ObjectId to an authorized Microsoft representative through a private, secure channel.

The recipient address was typed exactly as documented. The failure is the same as previously reported by other developers, but the current documentation still lists this mailbox.

Could the Windows App SDK team please:

1. Confirm the current supported and private channel for PFN-to-AppId mapping.
2. Provide a secure way to submit the complete mapping identifiers or route this request to the responsible team.
3. Correct the documentation if the mailbox is no longer valid.

Official documentation:

https://learn.microsoft.com/en-us/windows/apps/develop/notifications/push-notifications/push-quickstart

Similar reported issue:

https://learn.microsoft.com/en-us/answers/questions/2262455/notification-hub-cant-add-wns-service-invalid-wns