mail delivery failed

[asimsaleem]

We are using magicspam with our email using cPanel. So when we look into the magicspam logs tab and put one of our email user ID we get around 2381 rows, now point to get support on below points are as follow
1. Sender column is our user email ID
2. In recipient column it show unknow user ID, this unknow user changes after sending few mails
3. The Helo column showing our server hostname
4. The IP address of the hostname is different all the time and this is not our IP address.
5. Our email user get messages in his inbox with “Mail delivery failed:returing message to sender”
Please help us to diagnose and resolve this problematic issue, what steps to take to stop sending these mail,