About mailbox availability

[cemlouis]

Hi,

I am checking the given mails for my site registeration with the below function:

function validate_email ( $email, $check_domain=false ) 
{ 
    if (ereg('^[-!#$%&\'*+\\./0-9=?A-Z^_`a-z{|}~]+'.'@'. 
        '[-!#$%&\'*+\\/0-9=?A-Z^_`a-z{|}~]+\.'. 
        '[-!#$%&\'*+\\./0-9=?A-Z^_`a-z{|}~]+$', $email)) 
    { 
        if ($check_domain && function_exists('checkdnsrr')) { 
            list (, $domain)  = explode('@', $email); 

        if (checkdnsrr($domain, 'MX') || checkdnsrr($domain, 'A')) { 
            return true; 
        } 
        return false; 
    } 
    return true; 
} 
return false; 
} 

I don't know who wrote this one but works well, but this script checks only the domain availability. For ex: the domain "keew.com" exists but the "[e-mail]" doesn't exists. So How can I find this out? I mean I also want to know the mailbox is present or not?

Thank you,
Cem Louis