ICYMI - How to Write Successful Subject Lines

Content From: HIV.govPublished: August 20, 20194 min read


A line of people look at their cell phones

HIV.gov recently worked to identify components of successful subject lines, which we define as those that entice more readers to open an email. Unsuccessful subject lines, however, resulted in a lower number of open emails. Here are two of our lowest-performing subject lines:

  • Learn About How to Extend Your Social Media Reach at USCA 2018 — While this title has a call to action, the meaning was unclear. Did readers think it meant “Come to USCA and learn how to extend your reach”? Or did they interpret it as “How to extend your reach for the USCA conference”?
  • Hot Tips for Using Twitter (Part 1 of 3) — This title was too vague; we should have focused on something more specific. The reference to Part 1 of 3 may have also put readers off, since it implied that this blog post didn’t provide a full explanation.


In order to evaluate the success of our subject lines, we analyzed our metrics and specifically looked at the open rates of our 10 most recent emails. We also reviewed pageviews for our blogs. Once we had our list, we ordered it by most popular and looked at the blog post titles.

What Did We Find?

One of the biggest lessons we learned was that content really is “king.” We could do our best to draft a creative and compelling subject line or title, but if the content wasn’t interesting to our audience, the number reflected that. And the converse was also true--bland but clear titles that followed none of the rules did extremely well if the content was something our audience found helpful or relevant.

Next Steps

Finding out what works for your audience is critical. There are general guidelines (see below) but don’t be afraid to experiment! Subject lines are easiest to test using A/B testing, which is available through many email service providers. For titles on blogs, take advantage of repeat events. Do you blog about a conference every year? Look at which titles were most successful and which were least successful and apply it to the current conference. And to keep learning and keep your content fresh, try something new every year as well. One year you could try questions instead of statements. For example, instead of “Dr. X Discusses Advances in Y”, you could try “What Are the Advances in Y? Dr. X Discusses.”

Traditionally, our conference coverage titles were predictable and easy to write, “Research Highlights from Conference X 2018.” We hypothesized that conference titles with more content in them would do better, “Dr. X Discusses PEPFAR’s 15th Anniversary and Highlights of AIDS 2018.” To our surprise, the generic title did better.

We did an A/B test comparing our standard weekly email subject line. We compared subject line A “This week on HIV.gov” with subject line B, “A short newsletter: 3 blogs you may have missed.” Subject line B had a 7.1% open rate versus 5.4% for subject line A and a slightly higher click through rate. With tens of thousands of subscribers, the different of one or two percent are significant.

What Works Generally

Generally, there are ways of writing a subject that help shine a light on what your content can offer your audience:

  • Lead with the good stuff: Make sure the audience is clear on the subject of the blog. They may be very interested in the topic but if they don’t understand what the blog is about in a quick glance, they are less likely to read it.
  • Questions: Asking a question can get your audience thinking and if they are interested in the answer, they are more likely to read further.
  • Lists: For example, Top Ten Reasons to ….

So What?

Your audience may be different from the HIV.gov audience, but it’s worthwhile going through the process of reviewing what has worked in the past and testing new ideas. Try proposing multiple titles in the blog drafting and editing process, including ones that move away from dry and into fun and compelling. Think about it as a long-term study. Keep testing new hypotheses and see what works.

For more information on using data to inform your email strategy, check out this cross-post from USA.gov on A/B testing strategies.