Use this code inside your validator function:

var emailID = document.forms["formName"]["form element id"].value;
    atpos = emailID.indexOf("@");
    dotpos = emailID.lastIndexOf(".");
    if (atpos < 1 || ( dotpos - atpos < 2 ))
    {
        alert("Please enter correct email ID")
        return false;
    }

Else you can use jQuery. Inside rules define:

eMailId: {
    required: true,
    email: true
}

Use this code inside your validator function:

var emailID = document.forms["formName"]["form element id"].value;
atpos = emailID.indexOf("@");
dotpos = emailID.lastIndexOf(".");
if (atpos < 1 || ( dotpos - atpos < 2 ))
{
    alert("Please enter correct email ID")
    return false;
}

Else you can use jQuery. Inside rules define:

eMailId: {
    required: true,
    email: true
}

Use this code inside your validator function:

var emailID = document.forms["formName"]["form element id"].value;
   atpos = emailID.indexOf("@");
   dotpos = emailID.lastIndexOf(".");
   if (atpos < 1 || ( dotpos - atpos < 2 )) 
   {
       alert("Please enter correct email ID")
      return false;
   }

Else you can use JQuery also. Inside rules define:

eMailId: {      
    required: true,
    email: true
}

Use this code inside your validator function:

var emailID = document.forms["formName"]["form element id"].value;
    atpos = emailID.indexOf("@");
    dotpos = emailID.lastIndexOf(".");
    if (atpos < 1 || ( dotpos - atpos < 2 ))
    {
        alert("Please enter correct email ID")
        return false;
    }

Else you can use jQuery. Inside rules define:

eMailId: {
    required: true,
    email: true
}