We subscribe to Marketing Experiments.com for its marketing research results. We get to see data we can trust on issues of real importance to our clients—like this investigation into how to make the subject line of an email work best.

It’s common sense to say that emails reaching out to clients and prospects won’t work if they don’t get opened, but this experiment demonstrates that there are other things you can and should be measuring if you don’t want to leave money on the table.

Let’s look at the experiment, and what you should learn from it:

In this case, a florist wanted to increase the effectiveness of a “Thank you” email campaign to previous customers, and entice more of them to increase their purchases. They sent out two emails, with exactly the same content but different subject lines. Any differences in results could only come from the difference in the subject line.

They used an email service that allowed them to measure the “who opened the email and who didn’t” open rate, and the “who clicked through to a web site and who didn’t” clickthrough rate. Customers could also order on line, so they could also measure the sales resulting from the program. Both emails offered a 15% off special offer.

Subject Line #1 was “Thank You For Making Us Your Florist Of Choice”.

Subject Line #2 was “15% Off – Our Way Of Saying Thank You!”

Here are the open rate results: 20% of recipients of version #1 opened the email, but only 15% opened version #2, the one with the specific 15% Off offer. That’s a 26% difference.

Does that mean putting a specific offer in the subject line is a bad idea? Based on this, many people might think so—it looks at first glance that being too aggressive will put people off.

But look what we see when we dig a little deeper. 60% more people who received version #2, with the 15% offer, clicked through to the website. And version #2 ended up earning 56% more dollar sales.

Sure fewer of them opened the email, but they spent a lot more money.

What can you learn from this?

First, what you measure is important. In this case, if the florist only looked at who opened the email, she would have been badly misled. She might have planned future campaigns that practically guaranteed she would miss out on sales by 56%!

Second, testing is important. This advertiser had at least a 50-50 chance of guessing wrong with “gut feel”—and a potential huge business loss.

Third, if you use email, you need a batch or broadcast email solution that allows you to do this kind of testing and measurement. Don’t just send out to a huge “to” list—you will never be able to get the measurement and practical, business-building knowledge you need.

Elizabeth Walker and Ken BurginElizabeth Walker and Ken Burgin

Ken Burgin and Elizabeth Walker are the Marketing Masters, a full-service marketing and advertising partnership that helps build busy businesses.