From the desk of Nathan...
I was asked on X/Twitter today what subject line I've used has had the best conversion rate. Which is an interesting question.
Everyone wants little tricks to better engagement. Unfortunately nothing is that simple or cut and dry.
Conversion rate
The question was about what subject line got the best conversion rate—which I assume means the reader taking an action like buying the product. That's more complicated, so for now let's focus on open rate. The subject is to get the email opened, then the content is responsible for getting them to take the next step of clicking a link.
Looking through all my previous campaigns I found that the open rate is directly related to how many people I sent the email to. Emails to my entire list (nearly 18,000 subscribers) had an average open rate of 45-50% whereas some much more targeted emails had over 70% open rates.
The winner?
Back in August 2012 I sent an email to my entire list of 496 subscribers with a 83% open rate. The subject line was:
"Preview of The App Design Handbook"
Definitely not a revolutionary subject line. So what got the high open rate? Here's a couple factors:
It's one of the first emails I sent to a small list. Engagement tends to start high and decline over time.
Everyone signed up to hear about The App Design Handbook, this email promises pre-release content for the book. In other words I'm delivering exactly what I promised.
It included an image of the book sample chapter.
Wait, what? An image in the email matters? Yeah, a lot actually...
How using images increases open rates
Email marketing companies don't actually know when an email is opened. It's not like Gmail sends a notification to MailChimp to say "Hey, your subscriber opened the email."
You can only track two things in an email: if images were loaded and if any links were clicked. If either of those happen the email is marked as opened.
But if you use Gmail you've probably seen the "do you want to display images?" message. Gmail is looking out for your privacy and blocking all images unless it is from a trusted sender (or you directly authorize it).
If images are blocked, then the email marketing provider can't know if the email was opened.
An example
Let's say you send an email to 10 subscribers and all of them open the email. But if 4 of the 10 have images blocked (including the little tracking pixel), your email marketing provider will report a 60% open rate (instead of the technically accurate 100%).
Now let's say your email has an image in the body with a tantalizing caption. Those with images blocked will see an outline where the image should be and the caption, they have to click display images to see it.
If all 4 of the recipients who had display images off before turn it on to see this image, the tracking pixel will also be loaded. Meaning the open rate will now be reported (correctly) at 100%.
So you can always get your email marketing provider to report a higher open rate including images that people will want to see in the email.
Note this increases the reported open rate, not the actual open rate. In our example above the actual open rate was always 100%.
Link-bait subject lines
Certain subject lines do make your content more compelling to read or share. For example, one of the most popular articles I've ever written was titled "How I made $19,000 on the App Store while learning to code"
This is far more compelling than "Revenue from the App Store" because it does two things:
By sharing a specific revenue number in the title I show that this will be a detailed article that readers can really learn from. In a world where everyone is secretive with their salary numbers, sharing actual figures is compelling.
"While learning to code" hints at more of a story behind the article. $19,000 is impressive for a newbie, but would be a complete failure for an app development studio.
That really is a link-bait subject line. Not terrible, but I still find it a bit annoying. So I use that type of subject line sparingly.
Another common technique is "10 ways to do X. #3 is crazy!" This headline formula is now so overdone I just want to mock anyone who uses it. But these big sites use it because it is effective. Here's why:
People love list posts. A list implies it will be quick to read, deliver valuable insights, and be easy to share. The second part of the headline piques curiosity. Who cares about all 10 ways, I want to know about #3! You can start using headline formulas, but know they your readers will get sick of them pretty quickly. We've been trained that these formula headlines over-promise and under-deliver on the quality of the content. After being tricked into reading a few crappy articles, the formulas will stop working.
So instead focus on writing great content instead of using tricks.
Personal subject lines
My favorite method for writing subject lines (and emails themselves) is to write to a real person. Like my friend Gabe or my brother-in-law Philip. When writing a lesson I write it as though I am writing it to one person. Then when it comes time to write the subject line I put in something simple and natural.
I sent an email a month ago to everyone who had purchased Authority asking them to write a review. The subject line was simply: "A favor".
It went out to almost 1,000 subscribers and had a 70% open rate (an open rate will always be higher when sending to customers rather than just subscribers).
Wrapping up
The question we started with was, "do subject lines matter?"
Yes, they do, but not as much as you might think. The goal of a good subject line is to get the email opened, which may lead you to try link-bait style subject lines.
Instead you'll find that writing great content and building a relationship with your readers over time will have a much better impact on open rates than any tricky subject line ever will.