in_unique Validation Rule Help

This example https://codeigniter4.github.io/userguide...aceholders shows exactly what you're attempting to achieve. The only possible difference I see is that your statement for is_unique should be is_unique[users.email,email,{email}]. Though you should probably be using the user id instead to ignore the user's present email (as per the example).

In a more general sense. The user is opting to change their email. It doesn't matter what their previous email is. Whether they update it to a new value or the same value is irrelevant. The only thing that requires validation is that they aren't trying to use someone else's registered email.

Halberd | CodeIgniter Sandbox