Online web font services commonly offer five file formats to choose from: .eot, .woff, .woff2, .svg, and .ttf. The .woff and .woff2 formats have the best support when it comes to email, so we suggest using one or both of these formats when you can. The @font-face method is the only method that allows you to specifically choose what file format you’d like to import, making it the most bulletproof method for implementing web fonts.