@Andrew ,
Based on my understanding Onedrive sends emails automatically by default and there isn't a way to disable them. I've heard a lot of people mentioning false alarms with the Storage notification in particular. OneDrive retention and deletion - OneDrive | Microsoft Docs
In the Sharepoint admin center if you disable access delegation you might be able to remove those alerts.
I would recommend reaching out in the OneDrive forums to confirm though. https://techcommunity.microsoft.com/t5/onedrive/ct-p/OneDriveforBusiness