Fix mailbox export

can also export as csv now

src/views/users.js

@@ -258,7 +258,7 @@ angular.module('Application').controller('UsersController', ['$scope', '$locatio
                 return;
             }
 
-            var file = new Blob([ content ], { type: 'application/json' });
+            var file = new Blob([ content ], { type: type === 'json' ? 'application/json' : 'text/csv' });
             var a = document.createElement('a');
             a.href = URL.createObjectURL(file);
             a.download = type === 'json' ? 'users.json' : 'users.csv';