Participants details in Zoom Participants Fetch API not returning email and is fields for external attendees

Hi,
I am trying to setup an integration with Zoom. I am using the get past meetings participants API to fetch participants details.

While doing so I could observe that the email and the id of few participants are empty in the response. After further investigation, I could observe that these participants are not users of the same Zoom account.
Can I know on the reason why these fields are containing empty values for such participants. I would need the mail information to identify the external participants from the meeting. Is there a way to achieve the same.

Thanks in advance.