A Primer On Email Subject Line Testing

Subject line testing is not a new concept to email marketing or to this blog.  However, it is an important key to email marketing success. Subject line testing is easy to do and offers concrete results, but is often neglected.

Below is a typical inbox. Which subject lines best grab your attention? Which approach would work for your brand? Which one do you think is the worst performing? There's only way to know - test it out!


Keep in mind:

• Best-in-breed email programs consistently test their subject lines.
• It is important to verify your past findings and current theories about subject lines instead of making assumptions.
• If you can increase your open rates even slightly by optimizing your subject lines, the potential to increase click and transaction rates increases.

Do:

• Be clear and direct.
• Be short – keep subject lines to 50 characters or less.  (test this out to make sure shorter is better for your brand)
• Do tell subscribers what’s new in this message.
• Remind subscribers when sales/events are ending.
• Try wistful, fun or emotional subject lines.
• Test personalization, symbols (%, $) and capital letters. Also, I have seen pipes (|) used successfully.
• Set your subscribers' expectations during the opt-in process about what kinds of emails they'll be receiving.
• Try incorporating offer codes in the subject line.

Don't:

• Be deceptive.
• Be too long-winded.
• Deviate from your brand voice too much.
• Scream (use words in all CAPITAL LETTERS).
• Test once and then make long term decisions.
• Be afraid to have fun!
• Don't confuse newsletters with promotions. If your email is a newsletter, put the name and issue of the newsletter in your subject line. If your email is a special promotion, tell the subscriber what's inside. Either way, don't write your subject lines like advertisements.

Subject line recommendations and solutions are not a one size fits all solution. Discover for yourself about what works best for you and what does not work. Don't forget to document both your testing failures and successes. You do not want to forget what worked and did not work as you perform more tests. Also, you do not want to lose any testing knowledge as employees come and go.

Some subject line testing scenarios include:

• Short versus long.
• Mentioning a product type (shoes, savings accounts, cars, travel destinations).
• Mentioning of brand or style type advertised (Nike, Cargo Pants, Harry Potter, Rolling Stone, Jolly Ranchers).
• Using and testing placement of free shipping, percent-off or discount offers.
• Using language indicating urgency (limited time sale, 3 days only, etc.).
• Using language evoking curiosity or inspiration.
• Using first name personalization
• Including the company name.
• Using capitalization and abbreviations appropriately or intentionally inappropriately (Di$count 4U!).
• Including offer codes in the subject line.

A sample subject line test scenario: The 10-10-80 split

1. 10% of the subscriber list received Subject Line 1.
2. 10% of the subscriber list received Subject Line 2.
3. 80% of the subscriber list received the winning Subject Line.

The winner is most often determined by unique open rate but not necessarily all the time. In the case of including an offer code in the subject line, the winner might be determined by the number of sales generated by that offer code. In this case the subscriber does not even need to open the email for you to make a sale because they can often see the code from the preview pane alone.

If you are having a difficult time deciding what subject lines to create, get inspired by the content of the email or by your web analytics data (to see which content is recently popular on your site and which popular keywords are driving traffic).

When it comes to email marketing, the best subject lines tell what's inside, and the worst subject lines sell what's inside. But don’t take my word for it – you need to test, test, test this for yourself.