According to Clark, growing your opt-in email list can help you reach new customers, tap into new revenue streams, and minimize reliance on expensive social media marketing tactics. Growing your opt-in email list is important for plenty of reasons. Here are four that I've used personally to grow my own email list by more than 50,000 subscribers in the past five years. Your own email messagesHere's one way to grow your email list that's overlooked by almost all professionals: leveraging the signature file in your own emails. Instead of wasting the opportunity and encouraging them to follow you on Twitter, you can get them to subscribe to your email list ("Download her free 42-page Stand Out Self-Assessment Workbook and learn more at dorieclark.com.")

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