Irrelevant Content: Sending generic content to all subscribers can lead to disengagement. Poor Design: Emails that are hard to read or navigate can cause recipients to lose interest. Lack of Mobile Optimization: Many users check emails on their phones, so ensuring mobile compatibility is a must. Inconsistent Sending Frequency: Sending too often or not often enough can both be detrimental. Failing to Test: Not testing different elements of your email can lead to missed opportunities for optimization.