I had something similar happen in the past a long time ago on a x86 Solaris 10 mail server. An employee thought it was a good idea to share best quality/full resolution JPEG pictures of his new baby with the whole company. This swamped the mail server (load average was well over 700) while it chugged through delivering a 50mb email to 200+ employees. I forgot what process was the culprit (I think GNU Mailman) but after a couple of hours it finally settled down. I was amazed that could still SSH into it and figure out what happened.