By defaul, HubSpot offer only one Email contact field that we can validate the domain:
We can have situations that have a form with other contact personas, like this:
The issue is, we can’t validate other email custom fields. In this case.
1) HubSpot has a new type to custom fields, like email tpe
OR
2) When we create a custom field, we can select single line text type and in the rules validation, we have a email checbox rule
And in the forms, this will enable the functionality domain blocked