Deaktiver felter hvis checkbox er unchecked

JScript kode 

 function mail_auth_check() {
     var auth_check = $("input#auth_mail:checkbox:checked").val();
     if(auth_check == "auth_yes") {
         $("input#inputUsername").removeAttr("disabled");
         $("input#inputPassword").removeAttr("disabled");
     }
     else {
         $("input#inputUsername").attr("disabled");
         $("input#inputPassword").attr("disabled");
     }
 }

HTML kode 

 <form name="phpmailerServerSettings" method="POST" action="" role="form">
 <div id="form-inputServer" class="form-group">
     <label for="inputServer">Mailudbyder</label>
     <input type="text" name="inputServer" class="form-control" value="smtp.example.com">
 </div>
 <script>
     function mail_auth_check() {
         var auth_check = $("input#auth_mail:checkbox:checked").val();
         if(auth_check == "auth_yes") {
             $("input#inputUsername").removeAttr("disabled");
             $("input#inputPassword").removeAttr("disabled");
         }
         else {
             $("input#inputUsername").attr("disabled");
             $("input#inputPassword").attr("disabled");
         }
     }
 </script>
 <label for="mail_auth">Min server kræver godkendelse</label>
 <input type="checkbox" name="mail_auth" id="auth_mail" class="form-control " value="auth_yes" onchange="mail_auth_check()">
 <div id="form-inputUsername" class="form-group">
     <label for="inputUsername">Brugernavn</label>
     <input type="text" name="inputUsername" id="inputUsername" class="form-control" value="user@example.com">
 </div>
 <div id="form-inputPassword" class="form-group">
     <label for="inputPassword">Adgangskode</label>
     <input type="password" name="inputPassword" id="inputPassword" class="form-control" value="password1234">
 </div>
 <div id="form-inputSendFromName" class="form-group">
     <label for="inputSendFromName">Navn</label>
     <input type="text" name="inputSendFromName" class="form-control " value="Website navn">
 </div>
 <div id="form-inputSendFromAddress" class="form-group">
     <label for="inputSendFromAddress">Send fra adresse</label>
     <input type="text" name="inputSendFromAddress" class="form-control" value="noreply@example.com">
 </div>
 <div id="form-inputSSL" class="form-group">
     <label for="inputSSL">Min server kræver SSL kryptering</label>
     <select name="inputSSL" multiple required>
         <option value="ssl">Ja (SSL)</option>
         <option value="tls">Ja (TLS)</option>
         <option value="no" selected="">Nej</option>
     </select>
 </div>
 <div id="form-element-actions" class="form-group">
     <button name="phpmailerServerSettings" type="submit" class="btn btn-rad btn-primary">Gem indstillinger</button>
 </div>
 </form>