$('.email').each(function(l,i){
    var that = $(this);
    var thatOtherOne = $(this:after);
    $('<a>').attr('href', 'mailto: '+ that.html + thatOtherOne.css('content')).insertAfter(that);
    that.hide();
});
.email:after {
    content: "@mydomain.com";
}
<span class="email">info</span>
Hello again Stackoverflow!
This is my method against spam. Using CSS the :after selector and content I try fill my custom email in inside the <span> and the css adds the url. This doesn't make it clickable though, so that's why I try the above method using JS/jQuery. 
This sadly doesn't work because $(this:after); is not a valid selector. How can I change this?
 
    