AdWords API Sending client email in with headers gives error

Hi there,

Using php when I try and to in my clients account in the headers

$email = "<email>mydevemail@</email>";
$password = "<password>MyPass</password>";
$userAgent = "<useragent>SomeAgent</useragent>";
$token = "<token>MyToken</token>";
$clientacc = "<clientEmail>ClientEmail@</clientEmail>";
$header = $email . $password . $userAgent . $token . $clientacc;

I get this error
FAULT: 1
Code: soapenv:Server.userException
String: Login with this username/password failed.
Detail:

When I login to my google api account I can see my clientemail in there
and can view/acess that account. So how come I can access it via the
api?