There are ways to validate an email address domain using php such as this little function here.. its one way to sort out fakes. 

function isValidEmail($value)
{

    if (filter_var($value, FILTER_VALIDATE_EMAIL) == FALSE)
    {
        return 0;
    }

    //explode out firstpart and secondpart
    //local and domain names
    list($firstpart, $secondpart) = explode('@', $value);

    $firstLength = strlen($firstpart);
    $secondLength = strlen($secondpart);
   
    //check for lengths and if valid MX or A record
    if( $firstLength > 0 && $firstLength < 65 && $secondLength > 3 && $secondLength < 256 && (checkdnsrr($secondpart, 'MX') || checkdnsrr($secondpart, 'A')) )
    {
       
     return 1;  //valid
       
    }else{
        
         return 0; //not valid
          
         }
   
}// close function isValidEmail

Look at the EmailValidator class in ow_core/validator.php

maybe I'll give you a hint