Implemented suggestion in issue #341

pages/mailbox/mailbox.html

@@ -779,10 +779,12 @@
           if (clicks) {
             //Uncheck all checkboxes
             $(".mailbox-messages input[type='checkbox']").iCheck("uncheck");
+            $(".fa", this).removeClass("fa-check-square-o").addClass('fa-square-o');
           } else {
             //Check all checkboxes
             $(".mailbox-messages input[type='checkbox']").iCheck("check");
-          }
+            $(".fa", this).removeClass("fa-square-o").addClass('fa-check-square-o');
+          }          
           $(this).data("clicks", !clicks);
         });