To require the user to repeat their entry twice as an extra confirmation, go to field configuration in the DataPage wizard and select the field. Make sure the form element is set to Email for Caspio to validate the email format.

Now enable the check box Repeat for confirmation and type your label for the confirmation field:

Once enabled, the confirmation field automatically appears in your DataPage under the original email field:

Upon form submission, Caspio validates that both entries match and that they are a valid email address: