Issue
How to access sys_email table from scoped app in a flow designer
Cause
This was a conscious decision made by our dev team for security reasons to prevent the misuse of system tables from scoped applications.
Accessing system tables in Flow Designer can cause unintended system wide consequences, especially since flows can be executed with elevated privileges (Run As System).
Resolution
If you would still like to execute actions against system tables, you must create custom actions and try to modify from script