The document discusses five email marketing must-haves for conquering the inbox. It covers using HTML buttons instead of image buttons to increase engagement rates. It also discusses making emails responsive for mobile by adding proper breakpoints and formatting. Tips are provided for improving email deliverability such as lowering soft bounce thresholds and removing hard bounced emails. The importance of testing subject lines is discussed along with tips for writing subject lines. Lastly, the document describes how to run reactivation campaigns to reengage inactive subscribers.