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Get more opens on the mailing you’re sending right now

Why subject line split testing matters

Sometimes, we have to throw everything good we’ve learned out the window.

Examples: When there’s a “Real Housewives” marathon on TV but the house is a wreck or when there’s a spinach salad on the menu beneath a 10-cheese lasagna special.

Since Emma’s subject line split-testing feature launched last month, we’ve gleaned a lot from our own internal tests and those our customers have shared.

Below are four case studies that find laying out your cards isn’t always the best policy, a thoughtful subject line is worth the time spent on it and limiting your appeal can yield a yawn of a response.

Testing the level of detail revealed

Case Study 1: The appeal for help

One of our early split tests last fall was an email announcing Emma 25, a program that invites nonprofits to apply for free email service.

The variations – three of 'em – ranged from the less detailed "Help us find this year's Emma 25 honorees" to the more informative  "Emma 25 is here: help a small nonprofit win email for life."

The winner? A third variation, which landed somewhere in the middle of succinct and detailed: "It's Emma 25 time: We're giving away free email service!" 

This version boasted a 15% lift and, in the end, gained us 2,700 more opens.

Case Study 2: The sale announcement

Our client BOCA sent a split test in mid-December letting Sanctuary Medical Center customers know about holiday discounts, and they found that a little mystery about sale details entices the recipient.

The subject line “Limited-Time Pricing on Select Services” squeaked by with nine more opens than “FREE Clarisonic Offer + 15% Off Fractional Resurfacing & Great Gift Ideas.”

That narrow margin isn't nothing. When you play it out, sending the winning variation meant 193 more opens, a 13% lift.

They set their test to be autosend, as well, for a hands-off way to finish the test rather than manually sending the winning subject line to the remaining recipients.

There’s an increasing competition for your audience’s attention in their inbox. Looking beyond simply growing your audience list can help to achieve more positive brand engagement and interaction.

Testing the subject matter itself

Case Study 3: The monthly newsletter

There was an obvious winner in Belron US’s test: “Vehicle Maintenance Advice from Safelite AutoGlass” flounced the run-of-the-mill “Safelite AutoGlass Car Care Newsletter” subject line in an email about New Year’s resolutions for safe driving.

And it paid off: The winning subject line yielded 4,883 more opens, an 18% lift.

This is just a good, old-fashioned reminder that something, nearly anything, is better than using “newsletter” in the subject line.

A formula that works is being used here: “Vehicle Maintenance” could easily be replaced with “Interior Car Care” or “Roadtrip Checklist” in future emails, making the subject lines familiar enough to recipients, who are creatures of habit: I’ve been receiving and opening emails from One King’s Lane for months, but I’ve yet to purchase one product.

If we open one email and find something likeable, we’ll likely open the next.

For testing purposes, make your two subject lines distinct yet similar enough that you can glean useful information from the success of one and lesser-success of another. (In other words, don’t change capitalization and punctuation and branding and the offer.)

Case Study 4: The year-end email

“Brand new sets at our studio!” was the winning subject line over “25% Off Select Packages today and tomorrow only!” for Courtney Dellafiora Photography.

If your recipients don’t have the time, money or desire to purchase your product right now, you limit yourself by crafting a subject line that only reaches those in the market in the next day or so.

Keep in mind your goal and what you want to achieve in your email when thinking up your subject lines for split testing. Do you want an increased open rate? More clicks? To grow your list?

The more split tests you perform, you won’t just think you know the best one; you will know the best one, and come to better understand your audience’s habits in the process.

There’s no need to rely on your gut when it comes to first impressions, and don’t gamble with your profitability: test, test, test.

Happy testing, and keep us posted with what you learn: @emmaemail.


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