What's the difference between them? One-off communications versus prolonged, email-based interactions. For example, email marketing tools are excellent for one-off communications. You can use these tools for the one time you'd like to send someone an automated email response when they join a subscriber list, on their birthday, or when you promote a new product. But marketing automation tools are better suited for prolonged, email-based interactions. For example, you can use marketing automation tools whenever you want to guide someone from a subscriber list to a product purchase. Or you can send thank you emails or send new product promotions—all without having to lift a finger after the workflow is designed.
Beyond that, avoid using all caps, too many exclamation marks, and hyperbolic phrases ("ACT NOW BEFORE TIME RUNS OUT!!!!"). Poorly formatted HTML in your emails can also hurt how they’re handled. Every spam filter is different, so an email might pass through one filter but get flagged by another. For more comprehensive info on how spam filters work and how to avoid them, check out this guide by MailChimp.

Over time, the popularity of email marketing campaigns resulted in personal email inboxes that were overflowing with the latest and greatest offers. Email campaigns grew and people grew tired of them. Laws that allowed customers to unsubscribe breathed new life into email marketing campaigns as customers could easily pick and choose the companies they were interested in.
×