A font is a style of readable typography or text. They come in multiple styles and sizes and users can often personalize their font styles with colors and highlights.
However, not all fonts are safe to use in emails, as many email clients only support approved font styles. Some font designs render in particular email clients, but they may break in others. In these cases, email clients use a default font that might be jarring with an email design. Remember to use web or web-safe fonts while developing or drafting emails. Users can also create a font stack to select fallback options, should the first font fail to be supported by an email client.