Keep Subject Line Concise: Use 50-60 characters; avoid all caps or excessive punctuation Personalize With Placeholders: Use {customer_name} and {company_name} for personal touch Include Key Details: Always include invoice number, amount, and due date Make Payment Easy: Include the {payment_link} prominently in your email body Professional Tone: Match your brand voice - friendly yet professional Clear Structure: Use line breaks and formatting to make email scannable Contact Information: Always include {company_email} or support contact Test Before Storing: Send test emails to verify all placeholders and formatting work Mobile Friendly: Keep email width standard (around 600px) for mobile viewing Avoid Multiple Fonts: Keep typography simple - 1-2 fonts maximum