Subject Line
Last updated: March 2025
Definition
The first text a recipient sees in their inbox. It decides whether your email gets opened or buried. Good subject lines create curiosity, promise a specific benefit, or feel personal. Bad ones sound like marketing and get ignored or flagged as spam.
Why It Matters
Your subject line is your email's headline. 47% of recipients decide whether to open based on subject line alone. A weak subject line makes great email copy invisible. It's the highest-leverage element in any email campaign and the easiest to A/B test.
How to Improve
- Ask a question or tease a specific outcome. 'Quick question about your Q2 pipeline' beats 'Check out our new product.'
- Personalize with the recipient's name or company. Even basic personalization lifts open rates 20-30%.
- Avoid spam trigger words: 'free,' 'urgent,' 'act now,' 'exclusive offer.' Spam filters catch them and so do people.
- A/B test two subject lines on 10% of your list, then send the winner to the remaining 90%.