Using misleading subjects can lead to a variety of negative outcomes. First, it damages your brand reputation. When recipients open an email expecting one thing and find something entirely different, they feel deceived. This can result in a loss of trust, which is hard to regain. Second, misleading subjects can increase your unsubscribe rate and reduce your engagement metrics. If your audience feels misled, they are less likely to engage with future emails, reducing your overall marketing effectiveness. Finally, misleading subjects can lead to your emails being marked as spam or result in complaints, which can impact your email deliverability.