[DaveNGU]

Did you say this is in a custom file? If it is, there's no need to use $vbulletin->db->query_first - just use PHP.

But, assuming its not (in all honesty I haven't read all of this), try this..

$tmpname = $vbulletin->db->query_first("
SELECT email 
FROM " . TABLE_PREFIX . "user 
WHERE username = '" . $vbulletin->db->escape_string($username) . "'
");

$tmpnamer = $tmpname->row_array(); 

$usermail = $tmpnamer['email'];

echo $usermail;