To make user management easier for you, we have used the email as the main identifier. We need it to associate your user with the user of the app.
When a user downloads Traken App, it's necessary to create a new account, that it's validated during the sign up process. Once we have verified the user identity, you can add it just using the email address associated with his/her Traken App account.
You can add as many email addresses as you want, but we will never use it in any way.
We could contact Traken App user's only in certain circumstances, as password recovery or user activation.