Many common mistakes are made in email marketing, which can lead to low open rates, high unsubscribes, and poor engagement. Mistakes include overhyped subject lines, overlooking preheader text, using generic "noreply" addresses, sending emails with no value or too many calls-to-action, focusing on the product rather than the customer, lacking personality, containing too many images, missing the power of plain text, and not being consistent in email frequency. Additionally, failing to segment email lists, ignoring customer behavior, and requiring login to unsubscribe are major mistakes that can harm email marketing campaigns. By avoiding these common pitfalls and focusing on delivering value, personalization, and relevance, marketers can improve their email open rates, engagement, and overall effectiveness.