jQuery Validator - Override validation message for a boolean response from server

Question

I'm using jQuery Validator in order to process a simple form. Everything works as it should, but I would like to modify a little bit the validation process. I have integrated a small Ajax request to test whether the entered email already exists in the DB. The response is 1 in case the email already exists or 0 otherwise. I noticed that a label tag is created under the input field in case the email is not valid:

<label id="email-error" class="error" for="email">This field is required.</label>

Is it possible to override this generated label (after the jQuery Validator has validated that the provided email is valid), to indicate whether this email exists in the DB or not?
Suppose, for 1 the generated label will look like this:

<label id="email-error" class="error" for="email">This Email is already in use.</label>

This is the current configuration of the validator:

var $validator=$("#form-register").validate({
rules:{
     email:{
     required: true
     }
  }
});

This is the HTML form:

<form id="form-register" class="p-t-15" role="form">
   <div class="form-group form-group-default" id="email_div">
      <label>What's your email address?</label>
      <div>
         <input type="email" class="form-control" name="email" id="email" placeholder="Email">      
      </div>
   </div>
</form>

Answer 1

You can use the remote option here:

$( "#form-register" ).validate({
  rules: {
    email: {
      required: true,
      email: true,
      remote: "check-email.php"
    }
  }
});

Makes the email field required, an email and does a remote request to check if the given address is already taken. In addition, the http method is set to "post" and the username is sent alongside the email address.

$( "#form-register" ).validate({
  rules: {
    email: {
      required: true,
      email: true,
      remote: {
        url: "check-email.php",
        type: "post",
        data: {
          email: function() {
            return $( "#email" ).val();
          }
        }
      }
    }
  }
});