An email list that YOU COLLECT YOURSELF is worth its weight in gold. This can be accomplished by using a list manager on your site. List managers also provide the HTML coding for the form on the Gateway pages. A list manager collects the email addresses that are gathered with the form. Thus, your email list is collected. This might take some time so there are methods to use until you get your own email list built.
One way to build a mailing list is to do ad swaps with other list owners. The way this works is, you (as company A) have an email list that you send newsletters to and another list owner (company B) has a list they send newsletters to. Company A and Company B place ads on one another's mailing lists. Each of you is promoting the other's list.
You can rent or buy targeted email lists. The list you develop using your own customers' names is called your "house list." Of course, when you're first starting out, your house list is likely to be skimpy. To augment it, one way to go is rent or buy a mailing list. There are two ways to buy or rent a mailing list—approaching the company you want to rent from directly or using a list broker. Any company that emails information to its customers usually has a list manager, who handles inquiries and orders for the mailing list.
Another way to build an email list is to list your newsletter in all of the ezine directories.