Email Issues with Shopify

I have recently taken over the marketing for an existing Shopify site. I’m having an issue getting emails to go out from the ecommerce platform. We do get emails from the shopify account side but we don’t get any emails when we are testing customer emails. Shopify says they couldn’t be sent out. Also, the test accounts are automatically being unsubscribed by the shopify system. Can someone help me figure out what needs to be fixed?