Looking for Subject Lines that Stand Out? Use Inbox Insight

Recently, Return Path released a new ebook entitled Email Marketing for Retailers. While this ebook provides readers a guide to maximizing email ROI, more specific opportunities, such as subject line testing, can be evaluated and shared with Return Path’s competitive intelligence tool, Inbox Insight.

Before I discuss how you can use Inbox Insight to your advantage with A/B testing, first let’s walk through the product functionality and features.

Inbox Insight
Inbox Insight is Return Path’s competitive intelligence tool that allows you to increase subscriber engagement through competitive insights, while also providing visibility into engagement data from real email users within Return Path’s Consumer Network.

The Consumer Network consists of over two million email subscribers who voluntarily agree to exchange their email data in return for access to our many applications, for example Shopami. With the data we collect from the Consumer Network and the sending domain of any company, you are able to see how subscribers engage with different brands.

Inbox Insight is the perfect complement to your deliverability performance data. The additional Inbox Insight data provides a different perspective when thinking about specific email campaigns and marketing strategy decisions.

Now back to A/B testing.

What to Test
Inbox Insight can help you determine what you would like to test by providing you with visibility into your competitors’ emails all in a single view. For example, if your company is interested in sending out a new “Black Friday” campaign, you can leverage Inbox Insight to review “Black Friday” campaigns from the previous year to see how those campaigns performed. This information could be used to help define the new “Black Friday” campaign your company is interested in deploying.


Additionally, if you were not sure exactly what you wanted to test, you could use Inbox Insight to review industry and competitors’ subject lines over the last 18 months.

“Test to be the best!”
Now that you have determined what  subject line or previous email campaign will be your control group (or previous benchmark), next you need to identify what exactly are you going to test. Try adding some personalization to your subject line, or try altering the text or sentence structure.  For example, you might exchange commas in your subject line for line separators (|). For additional ideas on testing take a look at this blog that lists 50 ideas to help get you started.

In Inbox Insight you could create a “tag” for your “control” group. Tagging is a functionality in Inbox Insight that allows you to group and mark a subset of emails to see how those specific campaigns are performing. This is important because it allows you to focus specifically on one “tag”, topic or in this case your control and test groups. Secondly, as you deploy your test campaigns, you can create an additional tag labeled “test”.

Some other examples of “tags” in Inbox Insight are as follows:

  • “Black Friday”
  • “Holiday”
  • “Cyber Monday”
  • “Christmas”
  • “Spring”
  • “Fall”
  • “Winter”
  • “Mother’s Day”
  • “Black Dress”
  • “Shoes”
  • “Sale”

Lastly, be sure to have a sample size of five to ten campaigns in each the control and test groups to ensure you have a range or metrics to evaluate.


Analyzing Your Results

Ok, you have determined what you are going to test and created a control and test group — now you want to see how the campaigns performed. Inbox Insight can help with that as well. Using the Trends page in Inbox Insight, you can track the “tags” for both the test and control groups. Using the data in the Trends page, you can see how each group performed with metrics like Read and Forwarded percentage. You can also determine which day of the week, day of the month, and month each campaign performed its best.


With A/B testing, the key is to continually test new subject lines and tactics. With Inbox Insight you can continue to track and compare previous tests with new tests over an 18 month time period while also comparing your tests with competitor and industry metrics.

Moral of the story, continue to test and let Inbox Insight help you evaluate subject lines and modifications to your subject line format. Then view the metrics over time to see how the changes you have made are improving your subscriber engagement.


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