Understanding why customers open emails is crucial for optimizing open rates. The subject line is the first thing recipients see and plays a significant role in their decision to open an email. Personalization, such as including the recipient's name, can increase the likelihood of an email being opened. Additionally, timing is important; sending emails at times when recipients are most likely to check their inbox can improve open rates. A well-targeted email list ensures that the content is relevant to the recipient, which can also drive higher open rates.