In order to display custom fonts right in the email, the browser must receive font files with correct HTTP headers. If the server does not set required headers, some browsers can report errors in console or completely fail to display fonts.
To solve this issue your system administrator should apply the right CORS header for fonts on the server where they are placed.
Probably, your server is already configured, and you don't need to change anything. If not, you need to care about:
Correct mime-type headers
CORS headers — only if you serve fonts files & html pages from different domains
For IE, check that your http headers for the font files do not have
no-storeorno-cache.
Apache
To set right mime-types for font files, add these lines to config:
AddType font/ttf ttf
AddType font/otf otf
AddType font/woff woff
AddType font/woff2 woff2
AddType application/vnd.ms-fontobject eot
If you can't edit config, create .htaccess file in the folder with your project and add lines there.
For CORS headers add:
<FilesMatch
".(eot|ttf|otf|woff|woff2)"> Header set Access-Control-Allow-Origin "*" </FilesMatch>
Nginx
By default, Nginx has no default mime types for fonts and wrong mime type for .eot files. Go to the folder with configs and find where mime types are defined. Usually, that's in the mime.types file.
Search
.eotand string with it.Add strings below.
font/ttf ttf; font/otf otf; font/woff woff; font/woff2 woff2; application/vnd.ms-fontobject eot;
For CORS headers, add something like this to your host config
location ~* \.(eot|otf|ttf|woff|woff2)$ { add_header Access-Control-Allow-Origin *; }