To run a more secure Project, you can require that all applicants verify their email before they are able to apply.

When building your Project, the Require Email Validation checkbox will be checked by default:

Any applicant who has not already validated their email will be instructed that they must to do before they can complete your form. They will be given the opportunity to resend the verification email:

If you do not wish to require email validation from applicants, you can uncheck the Require Email Validation setting.