Refersion will automatically send emails, on your behalf, to your affiliates based on different triggers, such as receiving a new conversion. You can enable/disable these emails within your account. 

However, to provide this function we require an email using a private domain. For example, we cannot accept email addresses using public domains like Gmail, Yahoo, or Hotmail. 

By banning public domains, we assure our compliance with a universally adopted email authentication policy. In turn, this protects our clients, like yourself, from becoming subject to email hacks like sending potential spam to unknowing recipients.

You can read more about it here. 

To purchase a private domain email through Gmail, click here. 

If you are using Shopify, you can forward your email for free.