You should only use fonts that are generally available. Otherwise your signature will not appear as expected when people receive email from you. This is because fonts are not embedded.
Generally, in email signatures it is recommended to use with e.g. Calibri, Arial, Verdana, Georgia, Times New Roman, and Courier. These fonts are sometimes referred to as web safe fonts.
Web fonts on the other hand are not normally found on most operating systems, and while they allow for more creativity, many email clients do not support web fonts. If you use a web font that the receiving email client cannot display, then it will be shown using a fall back font, which will usually be Helvetica, Arial, or a generic sans serif font.