Is it mandatory to assign contact role to send dunning letters?

Hi,

I am trying to generate dunning letter for a customer. But the customer contact have e-mail id and does not have any roles assigned. When I ran the "IEX: Send Dunnings for Delinquent Customers", it is erorr out saying "Sending process failed: missing email address".

If I add contact role as bill to or Dunning I am able to generate the dunning letters and e-mail. Please let me know if Customer contact role is mandatory to generate dunning letters?

Appreciate your help.

Thanks,

Chaitanya