To be successful with email list marketing, the most important thing is that you have solid and current email addresses to send information to. Your email itself must also be compelling reading and there needs to be a solid call to action included with the email. Failure in any one of these areas will cause your campaign to yield few solid results.
You can also buy lists online, though some of these lists are not at all optimized but they are rather random addresses gleaned in various ways. You can also build email marketing list for the best email databases and sales leads.
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If you do supplement your list by purchasing or renting email lists make sure that you buy from a company that will provide you with addresses of people who have opted in to receive information on the topic you are targeting.
If you have a website, you can offer newsletters, free e-books and other incentives to get people to sign up for. There are many different ways to compile an email list. Make it as easy as possible for them by simply requiring they leave their name and email address and require that they confirm their request after receiving an initial email.
This way you will ensure that the addresses belong to people who genuinely are interested in what you have to offer, and that they made a conscious decision to pass on their contact information to you. These are the people who will be more likely to read and respond to your follow up emails.