For those who open the email and see the offer directly from you and all you simply did was advise them of the program. You raise your profit mailing list margin from that email versus losing money because you did not have a mailing list. How do you build your list? You want to build your list from your target market that would be interested in your product or service and to get them to your site.
Start with the end in mind, and consider what issue or problem they are having that your product or service can solve for them. Or it may not necessarily be a problem or issue, maybe what their interests are, but the goal is to ensure there mailing list is a market for it and build your list from those people. With that in mind, you are now able to create compelling content that will position your site in the search engines which would drive traffic to you.
When the visitors are on your website, you can offer the chance for them to join your mailing list, so be sure to have an opt-in or a signup page mailing list and let them know you will be sending You can also offer something upfront for them to opt-in as a special offer. Most people are aware you are selling something, but you want to set yourself apart from other marketers with a under-promise over deliver type of philosophy.