Find
Code:
$messages = $DB_site->query("SELECT privatemessage.*,touser.username AS tousername,fromuser.username AS fromusername,icon.title AS icontitle,icon.iconpath FROM privatemessage,user AS touser,user AS fromuser LEFT JOIN icon ON icon.iconid=privatemessage.iconid WHERE privatemessage.userid='$bbuserinfo[userid]' AND folderid=0 AND touser.userid=privatemessage.touserid AND fromuser.userid=privatemessage.fromuserid AND messageread=0 $ignoreusers ORDER BY dateline DESC");
in usercp.php and remove the text in red.
That will show the entire contents of the inbox.