Subject line testing is overused — but sometimes it makes sense. Like in this real world case study, where a small tweak yielded a nice win.
In this test for a niche B2C ecommerce company, we changed just one thing, the order of the copy in the subject line — and saw revenue-per-thousand-email-sent (RPME) jump 14.4%. No fancy segmentation. No redesign. Just a strategic rewording.
Here’s how it played out.
The Setup: Holiday Promo, Day 9, Subject Line Test
The company was in the thick of a “12 Days of Christmas” campaign. Each day brought a new offer, a new email, and a new subject line to match.
The original subject line (the control) led with the “Day 9” language, then dropped the discount offer at the end. The test flipped the order, putting the 20% discount front and center, within the first 25 characters.
Simple. Smart. Effective.
The Results | Day 9 Subject Line Test
Same creative. Same offer. Same list. The only difference? Where the offer appeared in the subject line.
That 14.4% lift didn’t require any additional send volume, budget, or development time. (ROI called—it’s impressed.)
And lest you think a 14% lift isn’t much… every little bit helps. Your team can use this tactic on every email you create going forward — and what would a 14% increase in overall revenue do for your company’s bottom-line?
Why It Worked
Inbox space is prime real estate—especially on mobile, where you’ve got roughly 25 characters before the cutoff. If your offer lives past that point? It might as well not exist.
Leading with the offer works because:
- Instant Value Recognition: The reader doesn’t have to hunt for the “why should I care?”
- Visual Impact: Numbers and discounts jump off the screen.
- Better for Scanners: Most people skim subject lines. Make the benefit unmissable.
Further analysis showed that most of the lift was caused by higher average order value (AOV) — our AOV on the test was nearly 32% higher than we saw on the control.
Takeaways for Future Campaigns
This wasn’t a one-day anomaly. It’s a nudge to revisit how you write every subject line going forward.
Your action items:
- Review promotional subject lines: Is the offer buried?
- Make the first 25 characters count; lead with value.
- A/B test other subject line copy: What else can you front-load for stronger performance?
Final Thoughts (and a Friendly Rant)
This wasn’t a big change. But it was a smart one. It’s a great reminder that sometimes, optimization isn’t about overhauling your strategy—it’s about tightening the screws.
So before your next send: Look at your subject line. Is the best part upfront?
If not, time to fix that. And here are a few more tips…
Until next time,
jj
Jeanne Jennings is a recognized industry expert, consultant, trainer, speaker, and author on email marketing strategy and tactics. In 2001 she founded Email Optimization Shop, a boutique email marketing consultancy; she is their lead strategist. Email Optimization Shop helps organizations make their email marketing more effective and more profitable. Learn more at www.EmailOpShop.com.
