jQuery Forum

$('#enquiry').validate({

  rules: {

    Email: {

    }

  },

  messages: {

  Email: "Enter valid email"

  }

});

i this case Input Email couln't be blank (required: true)
<input type="text" name="Email" value="Your Email" onFocus="doClear(this)" onBlur="doDefault(this)"/>

$('#enquiry').validate({

  rules: {

    Email: {

    }

  },

  messages: {

  Email: "Enter valid email"

  }

});

 function doClear(theText) { if (theText.value == theText.defaultValue) { theText.value = "" } };
 function doDefault(theText) { if (theText.value == "") { theText.value = theText.defaultValue } };
<input type="text" name="Email" value="Your Email" onFocus="doClear(this)" onBlur="doDefault(this)"/>

In this case we need just check email, phone or other conditions only to be valid if they typed by user and not blank or default.

email: true = valid email (could not be blank by defaul itself);
By default (email || phone || card || other ) methods not valid even if not required.

Suggestion:
jquery.validate.js
  email: function(value, element) {
   // contributed by Scott Gonzalez: http://projects.scottsplayground.com/email_address_validation/
   return this.optional(element) || /^((([a-z]|d|[!#$%&'*+-/=?^_`{|}~]|[ -퟿豈-﷏ﷰ-￯])+(.([a-z]|d|[!#$%&'*+-/=?^_`{|}~]|[ -퟿豈-﷏ﷰ-￯])+)*)|((")(((( | )*( ))?( | )+)?(([
--]|!|[#-[]|[]-~]|[ -퟿豈-﷏ﷰ-￯])|(([
-  -]|[ -퟿豈-﷏ﷰ-￯]))))*((( | )*( ))?( | )+)?(")))@((([a-z]|d|[ -퟿豈-﷏ﷰ-￯])|(([a-z]|d|[ -퟿豈-﷏ﷰ-￯])([a-z]|d|-|.|_|~|[ -퟿豈-﷏ﷰ-￯])*([a-z]|d|[ -퟿豈-﷏ﷰ-￯]))).)+(([a-z]|[ -퟿豈-﷏ﷰ-￯])|(([a-z]|[ -퟿豈-﷏ﷰ-￯])([a-z]|d|-|.|_|~|[ -퟿豈-﷏ﷰ-￯])*([a-z]|[ -퟿豈-﷏ﷰ-￯]))).?$/i.test(value) || $.trim(value).length == 0 || element.defaultValue==value;
  },