Email marketing is an important staple of marketing communications. Emails from companies to customers may be promotional in nature, to drive short-term purchasing, or relational in nature, for customer relationship management (CRM) and brand-building objectives. Emails are also issued when customers have opted in to receive alerts and notifications. The authors posit that these different types of emails (promotional, CRM, alerts) reflect both overt and more subtle attempts at persuasion and are associated with different levels of persuasion knowledge. Insights from the persuasion knowledge model ( Friestad and Wright 1994) and advertising wear-out are offered as explanations to understand consumer response to different types of emails. The authors test a model comparing the relative effectiveness of these types of emails on the email opening rate, the spending amount, and the shopping cart abandonment rate. They show that emails associated with relatively lower levels of persuasion knowledge are the most effective at increasing the opening rate and spending amount but are counterproductive for reducing shopping cart abandonment. In contrast, emails that likely trigger higher levels of persuasion knowledge are better for reducing cart abandonment. Alert notifications are mostly ineffective at driving our focal outcomes. The authors show that email effectiveness varies over time and is different for each type of email. They assert that combinations of specific email types, if strategically managed, can be used to enhance the spending of customers who opt in to receive specific alert messages.