Subject Line Length
Keep subject lines under 50 characters to ensure they don't get cut off on mobile devices, where over half of emails are opened.
Spam Trigger Words
Words like 'Free,' 'Act Now,' or 'Winner' are heavily penalized by spam filters. Avoid hype and focus on clear, direct language.
Capitalization
Using ALL CAPS is a major red flag for spam filters and is perceived as shouting. Use standard title case capitalization.
HTML Size
Gmail clips emails larger than 102KB, which can hide your content and, most importantly, your unsubscribe link. This is a major compliance issue.
Text-to-Image Ratio
Emails that are mostly images with little text are a classic spam tactic. Aim for a healthy balance, like 60% text to 40% image.
Compliance Links
A visible unsubscribe link and a physical mailing address are legally required by regulations like the CAN-SPAM Act.