A web page's or an email's design can be made more colorful and appealing with the aid of Cascading Style Sheets (CSS). However, because of how email clients "read the code," dealing with HTML emails that contain CSS can be difficult.

In this article, we'll go over the key ideas behind utilizing CSS in emails and look at some practical examples that show how to do it.

Why is CSS so Crucial for HTML Emails?

Here are some explanations of why CSS is crucial for HTML emails.

1. Branding Aspects

Colors are a crucial component of branding because they help maintain a unified aesthetic that affects how appealing a web page is. It gives you the resources you need to make professional-looking business emails, especially marketing ones.

2. Responsive design

The writing of CSS follows the Responsive Web Design (RWD) methodology. The styles are all set in one place, making it easier to create a responsive email that will change appearance based on the device being used to read it.

3. Better conversion

A collection of email templates that serve as your product's "packaging" can be created using CSS. In emails, using CTA buttons, visual hierarchy, and basic CSS animation can be a great way to nudge the reader into taking a positive action that produces quantifiable results.

Can You Avoid Using CSS for HTML Emails?

There is no question that an email can be created in plain HTML using only text and no CSS. An email that includes CSS may be larger. However, the size has no impact on deliverability or any other aspect of it. When sending a straightforward transactional or confirmation email that serves only to deliver information and necessitates little to no user action, it is possible to minimize the size of the email using CSS.

Let's examine the various CSS types and determine which are most appropriate for emails.

Types of CSS for Emails

Inline, embedded, and external styles are three types of CSS. Each technique slightly differs and is suitable for various purposes. Let's examine each one in more detail.

1. External CSS

External CSS allows you to make changes in one location and updates the associated HTML pages. You just have to attach the CSS code file to the head>/head> section.

For websites, this is acceptable, but it won't work for emails that use SMTP servers. This approach speeds up page loads while streamlining maintenance. Emails call for a different style of technique.

2. Internal or Embedded

Embedded CSS, also known as internal CSS, is another frequently used CSS type. With this technique, the actual style code is put right inside the and tags of the HTML file. Even though a preponderance of them was updated after 2016 to support it, only a small percentage of email clients have CSS support for the embedded method. Users still use outdated email clients or those that don't support them and don't display errors in emails properly by leaving the and tags in place.

3. Inline

An HTML email with inline CSS practically renders flawlessly on email clients.

Currently, inline CSS is considered a "bad idea" because it is difficult to maintain, lacks reusability, and restricts the use of selectors. Additionally, since inline CSS necessitates styling each HTML element separately, it takes up developers' time. The best solution to this problem is to use an online tool that performs the conversion and saves time.


The tools converts the code above to:

Tools for Creating HTML and CSS Emails

Creating emails that display flawlessly across all devices and email clients is a difficult task, but using some of the tools on the market will aid you.

  • Mailchimp CSS Inliner
  • Responsive Email CSS Inliner
  • Litmus Builder

Test your CSS for email client support

While creating emails is one thing, testing them before distribution is something you should also do. In this circumstance, you require an email testing tool to speed up the entire email testing process. This program will serve as a secure environment for developers to catch emails from the preview stage, examine the content, and produce a thorough spam report. It also, of course, has an email HTML and CSS checker.

If any elements or tags are not supported, you can edit the email code, send it once more, and view a preview of how the updated email will look on a desktop or mobile device.


Designing HTML and CSS emails can be difficult for a novice. But if you enjoy the process and use the appropriate tools to create those emails, it doesn't have to be.