In marketing we call it A/B testing - much like DOE - changing a variable within your marketing to see what the customer responds to. Here's a blog post from hubspot that explains it pretty well. https://blog.hubspot.com/marketing/how-to-do-a-b-testing
We typically divide a list into 2, give different messages or design or both and then track to see which has the best results. You'll usually only want to test 2 at a time.
Let me know if you have any questions - happy to help