Server Relaying Spam - Help Needed

We'll also need excerpts from your /var/log/mail.log showing the relaying. Also, according to the docs, rejectrblclient is only valid in smtpdclientrestrictions. mapsrbldomains is obsolete (maybe depending on what version of postfix you're running; you didn't tell us). You have a default permit action in smtpdrecipientrestrictions; I would change that to reject. Adding 'smtpdsaslauthenticated_header = yes' to /etc/postfix/main.cf could help if a mailbox password has been cracked (this will add a header detailing which mailbox account was used to send spam) - again, only useful if a password has been cracked.

I see your port 25 is tcpwrapped currently; have there been any more reports of spam? If so, this could be a trojan sending spam, or a wordpress/drupal/other install gone rogue.

Hopefully this will give you some place to start.

Edit: recommend you leave the paste up until your problem is solved. When I saw it, it had 2 hours left.