This Plugin => JQuery Validation Plugin

What I'm trying to do its to validation some input fileds, that will contain a NameServer which has the next structure ns1.hoster.com y got a pattern to detect if the user it writing a domain ^([a-zA-Z0-9]([a-zA-Z0-9\-]{0,61}[a-zA-Z0-9])?\.)+[a-zA-Z]{2,6}$ that i put into de input but a friend told me that can be erase if you inspect the element and recommend to use JS.

I found this on StackOverflow it's not exact what I want but would be great if someone can tel me anything helpful.

Custom Validation Rule

//custom validation rule
$.validator.addMethod("customemail", 
    function(value, element) {
        return /^([a-zA-Z0-9_.-+])+\@(([a-zA-Z0-9-])+.)+([a-zA-Z0-9]{2,4})+$/.test(value);
    }, 
    "Sorry, I've enabled very strict email validation"
);

Adding Rules

rules: {
                    email: {
                        required:  {
                                depends:function(){
                                    $(this).val($.trim($(this).val()));
                                    return true;
                                }   
                            },
                        customemail: true
                    },

Any advice, hint or tip?