Thank you for reaching out to the Community! It's important I point out that Constant Contact is an email marketing service. Because of this email address are needed for tracking contacts, sending campaigns, or signing-up to an event. I apologize, at this time there is not a way for an attendee to sign-up without an email address. It is however a feature request we have tracked in your account. As a workaround, we suggest using a fake email address as a placeholder for these registrants.