1. Ignoring Subscriber Preferences: Failing to consider when your subscribers are most likely to engage with your emails can lead to lower open rates. 2. Sending Too Frequently or Infrequently: Bombarding your audience with too many emails can lead to unsubscribes, while sending too few can result in disengagement. 3. Not Segmenting Your List: Sending the same email to all subscribers without considering their different time zones and preferences can reduce effectiveness.