Candidate Didn't Provide An Email While Applying Even Though Field is Required-How Did This Happen?

Summary:

Email is a required field, yet we had an ex-employee to apply, and when the Recruiter attempted to email them the offer letter, they got an error message that said "Emails can't be sent, the candidate didn't provide an email."

You can either start an application with an email or a phone number. So, in a lower environment, I tried using the phone number to start my application to see if I was able to skip adding an email as an ex-employee, but it still asked me for my email to confirm who I was. How did this person get by without adding an email address?