Typically, we use standard fonts for emails because custom fonts are not always supported by the end user’s email client. If it isn’t supported by the email client, it will revert the font to an email-safe font.
*Email-safe fonts: Arial, Century Gothic, Courier New, Garamond, Georgia, Helvetica, Impact, Lucida, Times New Roman, Tahoma, Trebuchet, Verdana
Email Client Support: https://www.caniemail.com/features/css-at-font-face/