Conducting A/B Tests: Subject Lines

May 6, 2009
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Ask any email marketer and they’ll likely agree that testing subject lines is a good practice… but ask them if they are running split tests and you’ll probably end up with a number of good excuses – our list is too small, it’s hard enough to come up with one good subject line, there’s not enough time, we’re not sure it’s really worth it or they simply don’t know how.

A good friend of ours had those same thoughts, but then he learned that a simple A/B split test could lead to additional ticket sales. He was marketing tickets for Friday events; his average open rate was 14% and he mailed three times a week. Then started testing his offers – two small groups would get the same offer but a slightly different subject line. The better performing subject line drove the rest of the email list; over the course of ten weeks he has sold 7,200 extra tickets due to the slight increase – average of 3% per send.

Keep these suggestions in mind when it comes to choosing a subject line – Don’t wait until the end to come up with a subject line for your campaign, start with a concept and post it so that your team (co-workers) can give input. Take their suggestions and start narrowing down the top two..


Ask any email marketer and they’ll likely agree that testing subject lines is a good practice… but ask them if they are running split tests and you’ll probably end up with a number of good excuses – our list is too small, it’s hard enough to come up with one good subject line, there’s not enough time, we’re not sure it’s really worth it or they simply don’t know how.

A good friend of ours had those same thoughts, but then he learned that a simple A/B split test could lead to additional ticket sales. He was marketing tickets for Friday events; his average open rate was 14% and he mailed three times a week. Then started testing his offers – two small groups would get the same offer but a slightly different subject line. The better performing subject line drove the rest of the email list; over the course of ten weeks he has sold 7,200 extra tickets due to the slight increase – average of 3% per send.

Keep these suggestions in mind when it comes to choosing a subject line – Don’t wait until the end to come up with a subject line for your campaign, start with a concept and post it so that your team (co-workers) can give input. Take their suggestions and start narrowing down the top two or three possibilities. Even if your list is too small to do a split test, choose a few subject lines and have your team bet on their favorite one, by keeping others engaged (especially your front-line) you’ll build interest and solicit their best input.

Your subject lines should be persuasive and have some intrigue (without being deceptive.) If you’re selling, numbers work very well – include the price (lowest possible) or the number of seats remaining. Make it timely – include a deadline, sell-out date etc. to create a sense of urgency.

There are times you have to rush to get a message out, leaving you no time to test. You could remedy this by running a test amongst friends, maintain a list of first responders – people who give you feedback on your offers, send it to them first or simply ask them for their opinion.

We Test Too
For our upcoming Service In Action call on Deliverability (May 29) we did a subject line test on the call invitation/ announcement – Deliverability: Unlock the Mystery and Mystery no more, Deliverability Tips and Tricks. Which of these works best for you? Let us know either through a comment or live on the call while learning about deliverability best practices.

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