Cold Email: Email content font

So my question is how do I create text blocks on email in a typeface which isn't listed as standard?

I've definitely seen it done. There's a platform called Moveable Ink which creates it in CSS and Java and at point of send converts it to a type of image so you don't loose your font style, but what are the other ways?

From a brand consistency POV obviously having the font matching is pretty essential, so I need to work out how (without using images)