Hello, thank you for reaching out to Microsoft Q&A.
The email you received is indeed SPAM. These kinds of threat or phishing emails are quite common, and you can even find examples of such spam messages online. Microsoft has several AI-based filters in place to block SPAM emails, however, some emails may still slip through cracks.
In this situation, please do not reply to the email, click any links, or download any attachments. If you have enough OneDrive Storage and your account is active, you can safely ignore the message, just mark it as SPAM and move it to your Junk Email folder.
Meanwhile, make sure your account has a strong password and is protected with two-factor authentication. Using the Microsoft Authenticator app would be the best and most secure option.
Note: Your OneDrive data will only be deleted if you exceed your storage limit and if your account remains inactive for more than 6 months without any changes to the OneDrive storage.