A/B testing, or split testing, is the process of testing two different emails (or style of email) to see which will produce the best results on a mass-scale. Typically, the system for A/B testing consists of designing two marketing emails and sending each one to a small subset of your email list. The CTR (click-through-rate) can be tracked via Google Analytics, then the results are tallied and whichever campaign was more successful is used for the remainder of the email list. Google even includes an A/B testing tool in their GA suite.
Be sure to compose each email carefully before starting the test. If you decide you want to change something about one of the emails or need to correct a mistake, keep in mind that this will skew the results and will likely throw off your numbers and the data will not be as useful.
You can use A/B testing to evaluate different subject lines, test visual design, the use of images in emails, different promotions including sales vs. coupons or HTML vs. text emails. Just about any factor of a marketing email can be tweaked for better results by using A/B testing. Using A/B testing, you can even test different “from” email addresses to check about whether a particular persona or address results in a higher CTR.
As with all marketing, email marketing benefits from more testing data and a more precise marketing strategy. GIve A/B testing a shot and let me know about your results!