When creating your own HTML Email Design System, you may want to use a custom font beyond the standard ones available. When working with brand guidelines where you need to use a custom font, it's always best to use a custom font with a solid fallback in place.


Email client support

The first consideration to take into account when working with custom fonts is that email client support is patchy. The following email clients support custom fonts:

  • Apple Mail
  • iOS Mail
  • Samsung Mail
  • Outlook.com

It's important to define a font-stack when using custom fonts. This should include some standard system fonts to make sure that your email renders in clients which don't support custom fonts.


'OpenSansBold', Helvetica, Arial, sans-serif

To host your custom fonts, you can either use a service such as Google Fonts, or host them yourself. We can also host them for our customers - we'll need to see proof of your license before we can do this.


For situations where your custom fonts aren't supported, you should select fallbacks that are included on the majority of computers. These fallbacks define what fonts will be displayed if the email client doesn't support custom fonts.


CSS set up


The most reliable way to include a specific font into your email is to use @font-face. Below is an example of this in action: 


<style> @font-face { font-family: 'Festive', cursive; src: url('https://fonts.googleapis.com/css2?family=Festive&display=swap') } * { font-family: 'Festive', cursive; } </style>


When working with Outlook, we need to wrap this @font-face in a @media tag. This is because Outlook 2007, 2010 and 2017 don't support them.