Using web safe fonts in the signature

The font used in an email, and more specifically in an email signature, depends on the fonts installed on the user's device.

If you configure a signature with a font that is not installed on the user's device or the email recipient's device, a fallback font will appear in that user's signature. This is different from a web page, which can use a font available on the internet.

For emails, you should favour so-called "web safe fonts", which are fonts installed by default on most devices. For information, you can consult this list: CSS Web Safe Fonts (w3schools.com)