CentOS 5 + Plesk 8.6.5 I sent one email to my friend. I got bounce email saying: ============================== Hi. This is the qmail-send program at mymailserver.com. I'm afraid I wasn't able to deliver your message to the following addresses. This is a permanent error; I've given up. Sorry it didn't work out. < here are tons of email addresses that I didn't send> <here is the email header and contents that I sent to my friend> =============================== My friend got the email that I sent. How can it happen? Can anybody explain me? How can I protect that not to happen? My Plesk server relay setting is "authentication required POP3 (lock time 20 minutes) + SMTP" Please help me to solve this problem asap. Thanks.