Email address not found. Unable to send email as the Sales doesn't contain Email address.

Email address not found. Unable to send email as the Sales doesn't contain Email address.

I have created a custom sales module. In this I have fields for 4x contacts from a sales lead. This gives me up to 4x email addresses. Always the first contact email is filled in.

When I click on "Send Mail" it gives me error:

Email address not found.
Unable to send email as the Sales doesn't contain Email address.

The contact email fields are set as email fields.

Not sure how to solve this so I can email via Zoho?