Using “Free” in the Subject Line
Experiment No. 007
Email Spam Words
Do a search for email spam words and you will get a list of hundreds of words to avoid. Toward the top of those lists you will see the word “free.”
Typical spam words over-promise, sensationalize, and attempt to maniputate you into opening the email. Reading through the lists though can worry a person. Many of the “spam words” are words we use everyday to help people understand the value. Words like “shipping,” “sale,” or “free.”
It sounds like if you use one wrong word in your subject line your email will land in email jail, the spam folder.
But is this true?
Spam is Bad
Anyone who sends emails wants to keep them out of the spam folder. One in six emails gets sent to spam.
An email in the spam folder will disappear like a sock in the dryer.
This is a wasted opportunity, one we want to avoid.
Emails go to spam for many different reasons including:
Buying email lists
Not having an unsubscribe link or physical address on the email
Low Engagement
HTML email with bad code
Trigger words present another reason to get flagged as spam , but it is not as crucial as it once was. So much goes into deciding if an email is spam that using one spam word wouldn’t hurt, would it?
We added “free” to the subject line of an email. The subject line was accurate. We offered a free resource.
Did the email end up in spam box limbo?
Let’s look at the results.
Research Question: Will using “free” in the subject line improve email engagement? Will it affect the deliverability?
Hypothesis: The subject line with “free”will get more opens, clicks and conversions. Deliverability will not get affected with the use of the word “free.”
Test Element: Subject Line
Control- Get Your Legacy Planning Kit
Test- Get Your Free Legacy Planning Kit
Key Metric: Open Rate
Other Metrics: Number of clicks on call to action button, conversions, deliverability rate, abuse rate.
Sample Size: Used a 50/50 split
Control- 361,005
Test- 361,113
Results: The subject line with the added “free” did not have a significantly higher open rate. The open rate for the test was 0.5% higher. However, it did get more
Total clicks - 5%
Conversions - 14%
Also, the deliverabiity rate for both emails was 99.8% and the abuse (spam) rate was 0.02%
Application: Use “free” in the subject line and button copy when appropriate. It increases the clicks and conversions. It does not have a negative effect on the deliverability.
Future Tests: A good test will often lead to more questions. This test raised a few. New test ideas include:
Add “Free:” at the beginning of the subject line instead of in the middle.
Capitalize FREE or put it in brackets [Free]
Final Thoughts: No one wants their emails to land in the spam folder. Having a list of words to avoid in the subject line is helpful, but also dangerous. Many articles saying don’t use certain words are false. The best way to find out is to test it. If landing in the spam folder makes you nervous, consider sending a segment first, then make a decision based on those results.
If you use the word “free” in the correct context and have built a solid email reputation it is wise to use it.
