The email marketing success in the U.S. can partly be attributed to marketers' collective mastery of A/B testing. This methodology involves creating two versions of a certain medium and sending out the version that attracts more traffic. It also experiments with pairings of elements like subject lines, email content, and send dates/times.Regardless of what you hear about the supposed ""death"" of this old strategy, keep in mind that customers can't get a social media account without an email address. On top of that, people open their email when it comes to confirmation of transactions and the like. Email, in other words, remains a relevant medium.