I want to use customs fonts in email templates but why @font-face style is not supported by most of the mail providers
what to do now?
@font-face is not supported in some email clients, but not all. Depending on what fonts you're designing with, you could specify a font-stack the starts with a custom font and falls back to similar system fonts. Something like:
font-family: 'open sans', 'helvetica neue', sans-serif;
The email won't match pixel perfect in every email client, but does it have to? More info on email typography, web fonts, and fallbacks.
You can make an image of each text blog as Jeff suggests, but it's not a great solution that needs to scale.