Designing and developing an email that displays consistently for all users can be a difficult task.
Email clients such a Gmail, Outlook, Apple Mail, Thunderbird, Yahoo and others can each display your carefully-crafted marketing email differently. This is because each client supports different features such as cascading style sheets (CSS) or background images.
Code that can be written for a website isn’t necessarily supported in HTML emails. As Ira Trof states, “coding cross-browser/client HTML emails was like taking a time machine back to the ’90s.”
The best way to ensure your email renders consistently correct for all users it to stick with what are considered safe practices. This includes using tables and nested tables to define the structure and layout of your email and utilizing inline CSS while avoiding margin, float and position tags to define table cell, font and image styles.
For more detail on creating cross client emails, see Ira’s article on Medium.
A final thought: While we still recommend avoiding commonly unsupported elements in your HTML emails, you could utilize analytics to look at whether your subscribers typically use a specific client, for example, many businesses use Outlook, and design for the most used client among your audience.