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Lessons from a Marketing Experiment: Email Marketing Subject Lines

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One of the things I love about marketing is finding out how people react differently to different versions of the same message, and testing the results in a scientific way so you can learn something. We recently sent an email to promote a webinar we were holding. We sent three different versions of the email to three randomly allocated segments of our list, changing only the subject line and first line of the email message. Based on the results, there were some interesting findings.

Email Marketing Subject Line Lessons Learned

1) Don't use the word "Free"
As you can see from the results above, when we used the word free in the subject line and the email text, we got a lower open rate and click through rate. A lot of Spam filters use the word free as a factor in deciding if they should block a message or not, so it is likely that a portion of these emails just got blocked, accounting for the lower open rate. In other tests I have dome about a year ago, I saw that the use of the word free increased click through rates enough to compensate for the lower open rate, but that was not the case here. Sounds like the conventional wisdom of avoiding the word "free" is a good idea.

2) Don't use the word "Special" or other superfluous language

The word special did not affect our open rate, so it looks like that word did not cause the messages to get caught in spam filters more than other words. But, our click through rate for these massages was less than if we used a simpler subject line. This seems to be because people saw the messages but then did not click or act upon them because they viewed them as "spammy" (even if they did not get caught in a spam filter).

Seems to me like you want to keep your subject lines simple and focus on the value of what you are providing - hence why "Invitation to Internet Marketing Webinar" performed the best.

Have you run any experiments on subject lines? What have you learned? Leave a comment below so we can discuss.

Posted by Mike Volpe on Wed, Oct 24, 2007 @ 11:59 AM