“Keep It Simple, Stupid” means that design should be as clear and simple as possible. Avoid using multi-column designs that don't translate well to mobile etc. Design should never be a distraction, but it should help emphasize your main message of your email.
The key is to focus on the most important elements by thinking like the recipient. Imagining what it’s like to be them can help you to understand what they want and what they don't want. Take into account that simple and minimalistic email designs aren’t primitive. Quite contrary! Especially if your brand’s visual appearance is minimalistic, let the email design align with that.
Don’t forget that one version of the KISS acronym means “Keep It Simple & Straightforward”, meaning that don’t overuse images or any other visual element in your email design. Instead of focusing on the quantity of graphics in the email, focus on testing which type of visual element converts the most.
Testing designs can give valuable feedback which can help reach your objectives faster. We recommend to A/B test like there’s no tomorrow.
However, there are some elements that are especially important to the A/B test: colors, buttons colors, buttons shape and size, buttons location, image-heaviness, video vs. no video, etc.