This usually happens due to the catch_all ALIAS is sending all email that DOES NOT have a pop3 or being forwarded to another account. This means that any other email will get forwarded by the catch_all to the main ADMINxxxx pop3 account. To stop this from happening, you will need to login to your Site Admin, click on ALIAS on the left, click on edit beside catch_all and change the forwarding to go to site_blackhole. The site_blackhole is like the recycle bin for MS windows. This means that the email will be REMOVED and not forwarded to a user.