A new person will join your company next week. You enter Factorial, and decide to create his/her user account. You realize that, for Dani, the new addition to the Sales Team, you will have to re-use the mail of the previous Dani, a former employee who was part of the Support Team.
When you try to create the user with Dani's email, the email text field appears in red, since you previously created a user in Factorial with that same email.
When you see that you have an ex-employee with that same email, your reaction is to go to Employees, filter for ex-employees and try to modify the email to enable the new employee, but when you try you realize that you cannot perform this action.
The text field in the email is blocked, so you will not be able to modify this information yourself.
In these cases, you can write us to the support department at firstname.lastname@example.org, to modify it ourselves from our database, and thus enable that email to create the user of the new employee.