Sending follow-up emails to people who didn't open the first message can work well when done with care. Some people miss emails because they are busy or the message gets buried in their inbox. A gentle follow-up with a different subject line can give your message a second chance. It's better to keep this follow-up simple so it doesn't feel forced. Sending too many reminders can make people feel annoyed, which can lead to unsubscribes. Testing different timings also helps you understand when most people are likely to check their inbox. What kind of follow-up message do you think encourages more people to give the email another look?