The subject line is critical as it often determines whether your email will be opened. - Clarity and Relevance: Make sure the subject line clearly reflects the content of the email. - Length: Aim for around 40-50 characters to ensure it is fully visible on most devices. - Personalization: Use the recipient's name or other personalized information to make the subject line more engaging. - Avoid Spam Triggers: Refrain from using excessive punctuation, all caps, or words like "Free", "Urgent", etc.