Qmail Hi-load And Large Queue

here is my problem.. i am running qmail on a plesk control panel. my load average around 15.. when i quit qmail it drops below 1.. when i clear out the queue it drops below 1, then it slowly starts rising back to 15.. i ignored my queue for a little while and it stacked up to 26k in the local queue and 1k in the local queue. overnight it builds up to 2k in the local queue and 12 in the remote.. i thought a php script was exploited so i tracked down every script using the mail function that i thought might be doing it and disabled them. i noticed some difference but the queue is still building up rapidly.. i also altered the /usr/sbin/sendmail so it will log all mail sent and that doesn't pose a problem as only 10 emails have been sent via /usr/sbin/sendmail in the last 24 hours. i also tested my server for open relays via abuse.net and it passed the open relay tests. what else could be happening? all the email in the queue is spam.. where is it coming from? some is being sent to users on the server and some is not.. i am at a total loss right now, and really need to get this problem solved. thanks for any help.....