How to mask email addresses in test pod

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We have previously masked the email addresses in our test instance of Fusion so that work can continue but no emails are sent to staff.

I have used HDL to add the word TEST_ to the beginning of the work email address.

This HDL has worked successfully and in Manage person the email shows TEST_****@****.com, however, in security console the email address remains the standard member of staff's work email address which means they still receive email notifications.

How can email addresses in the users account be masked to stop any notifications being received by the staff?