content = "";
$.each(data.response, function(i, y){
$("div#userBox_"+id+" div#"+tab+"File").html(content);
$("div#userBox_"+id+" div#"+tab+"File tr.")
content="<table class='crmTable'><tr><th colspan='3'>"+y.email.email+"</th></tr>";
This .js code gives out this view

I would like to add a .attr(mailto) somehow to this…but I have no Idea how to do this.
I can’t speak to the rest of your code, but it appears what you want to achieve is as simple as adding the link to your output string:
I assumed you wanted a
mailtolink, and that “mailto attr” is just a mistake in semantics (there is no “mailto” attribute).