Which of the following has been shown to boost email open rates?

Personalization, such as using the recipient's name in the subject line, creates a more relevant and engaging experience, making recipients more likely to open the email. Strategic capitalization, like using all caps for a single impactful word, can draw attention to the subject line and make it stand out in an inbox. However, excessive capitalization can appear aggressive or spammy. Asking for something in the subject line can deter opens if it feels like a demand. Ambiguous subjects, while sometimes used for curiosity, often lead to lower open rates as recipients prefer clear expectations.