
Hi @Matt,
Thank you for posting in this community.
The email address of an alert is decided by the work email of user who created the alert.
If you want to change the work email of user, you can go to SharePoint admin center -> More features -> User profiles -> Find the user profile -> Edit the user profile -> Change work email of the user.
But we have no way to set the sender to be anonymous.
The alerts feature not only sends an alert but also informs the person receiving the alert who sent it. This is designed by SharePoint. For example, an alert sent when a file has been modified will help the person receiving the alert know who modified the file.
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