SQL how to unset the @

Question

I try to update my DB by using an email as key, but the @ sign in sql didn't work.

So, i tried also

""+':mail'+""';

So, how could i use the email with an @ sign as keyword?

$sql2 = 'UPDATE kunden SET anzahlung = 100 WHERE mail = :mail';

$stmt2 = $objDb->prepare( $sql2 );
$stmt2->bindParam(':mail',$_POST['payer_email']);

$stmt2->execute() ;