Oh and another fun thing! I eventually just emptied the OneDrive so Microsoft would stop bothering me. This was maybe six months ago or so. Microsoft confirms I am storing nothing there. Just a week or two ago I got yet another email begging for money because my OneDrive was apparently full. It was a genuine email, I went as far as checking the headers for SPF/DKIM. When I signed into onedrive, still empty!

Isn’t there a recycle bin?

Apple has something similar. One has to delete out of the hidden deleted items area — unless they want to wait a full month!

I suppose if you’re not paying them, your storage limit is zero, so if you have zero bytes there you’ve reached max capacity.

Anecdata, they might have had a system error. My Microsoft account that I use the free tier OneDrive on had the same email sent (you're over x% full, consider upgrading!). I suspected everything you did - eventually I logged in after verifying the email - nope, 5% usage or so.

I then went and deleted more stuff, but my money would be on a reporting glitch than a malicious money campaign.