Email Subject Line Craft & Best Practices
The rules behind subject lines that get opened - capitalization, length, punctuation, spam triggers and personalization. This hub covers the craft decisions that hold across every send, then hands you a generator to apply them. Start with the guides below, then draft and test variants on your own list.
Written & reviewed by Clover Elise Winter, Senior SEO Content Strategist & Technical Research WriterLast reviewed: Articles in this hub
Title case, sentence case or all caps? Learn which words to capitalize in an email subject line, how to handle "thank you", and the punctuation rules that apply.
100+ catchy email subject lines plus the power words, curiosity hooks and urgency triggers behind them - and which attention-grabbing phrases trigger spam filters.
The subject line rules that actually move open rates - length, capitalization, personalization, words to avoid, and the common mistakes that kill your campaigns.
The ideal email subject line length is 30-50 characters, or four to seven words. See character limits by device and client, plus what the research disagrees on.
More AI Email Subject Line Generator guides
Tested email subject line examples and templates by scenario - cold, follow-up, breakup, and more - with length rules and spam triggers that lift reply rate.
Why emails go to spam and how to fix it - authentication, sender reputation, list hygiene and spam trigger words, plus a deliverability checklist.
Email open-rate benchmarks by industry plus CTR, CTOR and unsubscribe rates, why Apple MPP inflates opens, and how to A/B test your subject lines.