We recently were asked to check the possibility of updating the SYSTEM user specifically the primary email field of it.
Usually, we use SYSTEM user to specify the plugin’s execution context for business requirements that needs elevation of privileges.
And also we can neither update it from the user interface nor it is recommended to update the SYSTEM user.
If we try to update the user through code, we’d get the below error message
Error updating Users – No modifications to the ‘SYSTEM’ or ‘INTEGRATION’ user are permitted. [See the Execution Plan tab for details of where this error occurred]
Hope it helps..