I have a website and an email marketing tool. My site domain(test.com) and my email makrketing subdomain(email.test.com), keep sending transactional and marketing mails to customers. I would like the customers, receiving these emails, on their respective email servers(e.g gmail, yahoo, etc) to be able to WhiteList our email domain and sub domain. Thus ensuring that all our emails reach the customer inbox.
Is there a tool, which I can configure to achieve the same, and the mention the link of the same in all our emails, as a customer opt in. It should also be as easy as a single click for the customer to opt in.