Makes the form refuse submissions from personal email providers, such as gmail.com, yahoo.com and outlook.com, by setting options.block_personal_email_providers to true. The providers come from a list ActiveCampaign keeps, so they need not be added to options.blocked_email_domains one by one; the domains on that list stay blocked as before. Blocking when they are already blocked changes nothing and succeeds. Use PUT /forms/{id}/allowPersonalEmailProviders to take them again. Preference Center forms take no typed email address, so this has no effect on one. Requires the permission to edit forms.