Gradient in emails?

Jumping right into your question here, this would depend on a few factors, such as which email editor you're using (Drag & Drop vs Code Editor), where you want to add the gradient, etc.

In general, the Drag & Drop editor does not support gradients for things like buttons and background colours, but you could add a background image with a pre-existing gradient if you'd like to. The Code Editor on the other hand allows you to write your own custom HTML / CSS, which would let you add gradients dynamically without the use of background images. This help guide talks about that in more detail, and has some compatibility charts so that you know which email clients support gradients once the email is rendered.

I hope this information is helpful!