Is someone spamming through me?

[Jody Cleveland]

Hello,

I'm running Mailscanner v.4.52.2 with postfix on a redhat 4.0 AS server.

Yesterday, I got over 5000 bounce messages from the server, all messages
trying to be send to a zipmail.com.br domain. In my logwatch message
this morning, I noticed this:

 120343658 bytes transferred
 53041 messages sent
 1 messages expired and returned to sender
 5 resent messages
 20271 messages removed from queue

I checked my server here: http://www.abuse.net/relay.html and all tests
for being an open relay were negative.

Any ideas what may be wrong?

- jody