Which of the following is NOT commonly considered a method of digital marketing?

Billboard advertising is not commonly considered a method of digital marketing because it relies on traditional media channels rather than online platforms. Digital marketing encompasses strategies that leverage the internet and electronic devices to promote products or services, which includes email marketing, social media platforms, and pay-per-click (PPC) marketing. These methods utilize digital technologies to reach consumers, engage them, and drive conversions online. In contrast, billboard advertising is a form of print advertising that targets consumers in physical locations and does not involve digital technologies, thus distinguishing it from the other options listed.