Identify vistior by tracking url

I have no clue what is it exactly “Identify vistior by tracking url”?

As it mentioned a Note: Email contact field have to be marked as unique indentifier and publicly updatable in Configuration.

How do I mark email as unique indentifier?

I have no clue what is it exactly “Identify vistior by tracking url”?
As it mentioned a Note: Email contact field have to be marked as unique indentifier and publicly updatable in Configuration.
How do I mark email as unique indentifier?

Thanks Kuzmany

Hi,
Is it possible to pre-populate a form with this method?

Cheers
Javier

The answer is here https://mautic.org/docs/en/forms/manage_forms.html