Email Subject Lines: Formulas That Actually Get Opened
Proven subject-line patterns, length guidance, and the preheader trick most senders forget — with examples.
Your email subject line decides whether anything else you wrote gets read. It is the one piece of copy every recipient sees, so it earns most of your editing time.
Formulas that work
- Specific benefit: "Cut your bounce rate in 3 steps".
- Curiosity gap: "The setting most senders miss".
- Personal + timely: "Your June report is ready".
- Question: "Still landing in spam?"
Keep it short
Aim for 30–50 characters so it survives mobile truncation. Front-load the important words; the first three rarely get cut.
Send email that actually lands in the inbox
API and visual editor, SPF/DKIM/DMARC out of the box, analytics and warm IPs. Free tier — 200 emails/month, no card required.
Do not forget the preheader
The preview text is a second subject line. Left blank, inboxes show raw HTML or "view in browser". Write it deliberately to extend the subject's promise.
Test, do not guess
Subject-line intuition is unreliable. Run an A/B test on a slice of your list and let data pick the winner. Sendersy has A/B testing built in. Try it free.
Writes about campaigns, segmentation and automation. Ran email programs for SaaS and e-commerce.
Read next
Email Open Rates in 2026: Benchmarks and How to Improve Them
What counts as a good open rate, why Apple Mail Privacy changed the metric, and practical ways to get more people reading.
Email List Segmentation: Send Less, Earn More
Why segmented campaigns outperform batch-and-blast, the segments worth building first, and how to keep them updated.