When it comes to email, marketers know that the effectiveness of messaging and content is nowhere near an exact science. There are so many ever-changing variables: design trends, your company's creative strategy, and even how people receive their emails. So, with all of these consistently moving parts, marketers are also keen to test any number of variables of content within their emails to know what's working. These tests allow you to hone in on what your subscribers are looking for and can lead to an overall higher performance from your email strategy.