Misspellings and poor grammar in email subject lines and content can negatively affect email deliverability and spam filter placement. While not always a primary factor, these errors contribute to a lower sender reputation by signaling unprofessionalism and potentially triggering spam filters. Internet Service Providers (ISPs) analyze content quality, and consistent errors may associate your domain with low-quality content. Additionally, machine learning (ML) filters look for patterns, making it difficult to predict what might trigger a negative classification, including incorrectly spelled words. However, the impact of misspellings is nuanced, depending on whether more bad mail than good mail exhibits the characteristic and the potential harm of misclassification. Therefore, careful attention to writing, proofreading, and maintaining a good overall content quality are essential to avoid being flagged as spam.