Email Marketing: Subject line test increases open rate by 10%


Every year, MarketingExperiments’ sister brand MarketingSherpa holds its annual MarketingSherpa Email Awards as a showcase to recognize marketers who designed email campaigns that exceeded expectations.

In today’s MarketingExperiments Blog post, I wanted to share a simple subject line test from a previous gold medal winner you can use to aid your email marketing efforts.


Winning back hearts and minds one email at a time

Travelocity identified a segment of existing email subscribers who had not booked for over a year and wanted to win back that segment’s business.

The team worked with StrongMail to develop an email campaign strategy to generate engagement, and drive conversion from the lapsed set of subscribers.

The StrongMail team started evaluating previous campaigns and testing offers.

One of the elements StrongMail used to test those offers was a subject line treatment offering a 10% discount incentive to the lapsed segment.

Here were the two subject lines:

Subject Line A: “Save an additional 10% for a limited time only.” (Shorter subject line with generic offer.)

Subject Line B: “As our valued customer, get an extra 10% off for a limited time only.” (Longer subject line with the “valued customer” message.)



Subject line B outperformed subject line A by a solid 10%.


What’s also interesting here is that when the 10% incentive was tested against a 15% discount, pictured above in a second round of testing, the increased incentive did not yield a significant difference in open rates.


What you need to know

A successful email marketing campaign requires more than identifying an unresponsive list. It also involves careful research of what has worked and not worked in the past and testing new approaches to engage a slumbering list.

The Travelocity and StrongMail teams were able to re-engage a significant percentage of those lapsed customers to generate incremental revenue that would likely have been lost to competitors.


Related Resources:

[Video] Email Marketing: Use website content to increase list size

Email Optimization: A single word change results in a 90% lift in sign-ups

Email Copywriting: Simplification, specificity, focus on customer generates 400% increase in CTR

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  1. Eric Sloan says

    Seems to me like the core of this test is the inclusion of “our valued customer” because it’s more personal.

    The trouble still remains that if someone is not looking to travel right away they would never open a subject line that has 10% off in it. That’s all fine and good for creating immediate sales, but it doesn’t allow for any customer connection to occur.

    Would love to see a test of a line like this:

    Just for you (thanks)

    I have a feeling it could improve even more on the test in this post by drawing more people into the email.

  2. James Maxwell says

    Did this have any impact further down the funnel for click and orders? That’s what I really care about.

  3. Web Designers Singapore says

    You are right Mr. John Tackett, now the emails and websites only plays a good role in marketing, the magic done by the internet signals always.. Nice post..

  4. direct marketing japan says

    WOW. You went with great points in your article. Keep update more often.

  5. Tim Suder says

    I clicked on here assuming there was something to be won and after considering the subject line matter intended toward a potential client/customer base, wouldn’t/shouldn’t all subject lines therefore insinuate the notion that if one were to click on it to inquire further as to the contents of the e-mail, they might possibly win something or get something for free? Doesn’t always work for me, but strategic e-mails directed toward the appropriate clientele containing the correct subject matter in the subject area seems like a no-brainer. Ahhh…access to the intended targets likes/dislikes, too much research.

  6. Ron Seawood says

    I believe the improvement of email b over a is due in part to the bonding words used in the subject line. “Valued Customer” term used give the customer a sense of connection with a company regardless of how many times they purchased in the past. The term “Valued Customer” also give you a sense of exclusivity, as if you are the only customer being spoken to at the time.

    Thanks for sharing the results of this test. I will make sure to place more bonding words in subject lines in the future.

  7. Niki Armstrong says

    Really awesome blog for email marketers.

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