When you get a user’s email address, prompt them to give you a confirmation. Double Opt-In email marketing sounds like it shouldn’t be more effective: after all, you’re asking a user to go through a two-step process when giving you their email address instead of one. However, a two-step process is crucial for weeding out spam signups. Email marketing is not just about the breadth of your email list, but also about the quality of the leads.