If you want to add your Affiliates to MailPoet mailists in WordPress, then all you need is Affiliates MailPoet Subscribers plugin. It is an extension for Affiliates, Affiliates Pro, Affiliates Enterprise from itthinx.com and MailPoet Newsletters from mailpoet.com.
With this extension you can automatically subscribe new affiliates in MailPoet lists. When a new affiliate registers to your site, he is also becoming a member of a subscription list called Affiliates. If the list doesn’t exist, it automatically creates it and then subscribes the new affiliate.