Email is the workhorse of the digital toolbox. Not only does it routinely outperform other channels, it's less expensive and more efficient.
The increase of mobile usage has been a challenge for senders however as smartphones have different dimensions and as a result, different challenges to create optimized experiences. According to Litmus, in fact, mobile now represents no less than 50% of where email is read. If you're not designing emails with mobile in mind, you're not taking full advantage of the email opportunities.
Emails, as such, need to be designed in a way that they can be interacted with and consumed easily on a mobile devices. Fortunately, there are many best practices which designers can abide by, and increasingly, frameworks to make development much, much easier. MJML.io, for example, is one of those frameworks and one that is definitely worthy of a closer look.
The framework, which you can try live here, essentially makes creating responsive-email a lot easier. MJML is essentially a markup language designed for responsive email coding. Its semantic syntax is quite straightforward and its standard components library shortens development time and tightens up the email codebase. There are several templates available to serve as inspiration. If you're looking to improve email marketing performance, MJML.io is an excellent place to start.