Send a copy of email with signing link

Hi everyone,

I'm using the Adobe Sign API to create an agreement for a user of my web app. They should be able to provide an email address of the party responsible for signing the document(it's often a different person). But in case they entered a wrong email, I'd want them to also receive a copy of the email with the signing link. How can I specify this CC email?

One thing I tried is sending it as a recipient set with multiple emails:

recipientSetInfos: [{

  recipientSetMemberInfos: [{ email: 'signer@email' }, { email: 'cc@email' }],

  recipientSetRole: 'SIGNER'

}]

But I'm getting an error 400 with "Recipient set is not enabled".