One of the most effective ways to get people to click and read stories is also the simplest: personalize content for them based on what they’re already reading.

To promote some of its biggest stories, The Washington Post has experimented with “pop-up” newsletters. Sent to the Post’s existing email subscribers (who don’t opt in), the newsletters are personalized based on readers’ interests and behavior. To promote its recent story about a Naval Academy teacher accused of sexual assault, for example, the Post emailed users who have read similar stories in the past. The Post has used the pop-up newsletters to promote eight stories since January.

The personalization brings another level of relevance to The Washington Post’s newsletters, said Jennifer Amur, the Post’s newsletters and alerts editor. “We’re trying to make sure that the readers who would be really interested in our most compelling pieces of journalism are actually seeing them,” she said.

So far, The Washington Post’s email personalization experiment is being used with third-party tools, but it plans to eventually bring the feature to Clavis, its content personalization tool. Inspired by Amazon’s own personalization engine, Clavis works by analyzing keywords and phrases in the articles that users read. Those keywords are then used to match users to other content that they might like. The tool, which powers the “Post Recommends” widgets on the Post’s site, has also been used to target native ads.

The emails themselves are simple. The email promoting “A Marine’s Convictions,” for example, features just an introduction, the first three paragraphs of the story, a link to click through to the full version, and links to share the story on Facebook and Twitter. The idea is to get readers to read the story, share it, or, ideally, do both, said Amur.

It’s an effective formula. Click-through rates for the personalized newsletters are three times the average and the overall open rate is double that of the average for the Post’s newsletters. (Amur wouldn’t give specific numbers.)

Those results show why personalization can be such a powerful tool if used properly. If publishers are better able to tailor content to readers, the thinking goes, then they also increase the chance that those readers will click through, and keep on reading once they do. The problem is that, while publishers see the potential in personalization, few have made it core to their distribution strategies.

But personalization is not the only way to increase the chances readers will click through in newsletters. While The Washington Post has taken the personalization route, publishers such as The New York Times have increased newsletter relevancy by creating vertical newsletters focused on niche interests and even individual columnists such as Nicholas Kristof. In February, the Times launched The Edit, a newsletter aimed at college students. The Washington Post has taken that route as well, with the launch of recent newsletter such as the animals-focused “Animalia” and “In Theory,” which is focused on opinion pieces.

While much of the publishing industry has set the bulk of its attention on Facebook, the power of the newsletter can’t be ignored, Amur said. “So much of what we do with the newsletters and email alerts and app alerts is to reach people where they are. People take their inboxes with them.”