Basic spam filtering in postfix

I was starting to set some basic spam control in our mail server (postifx in RHEL 3). So, based on http://www.unixwiz.net/techtips/postfix-HELO.html and http://www.freesoftwaremagazine.com/free_issues/issue_02/focus_spam_postfix/, I added to main.cf:

smtpd_delay_reject = yes
smtpd_helo_required = yes
smtpd_helo_restrictions =
        permit_mynetworks,
        warn_if_reject,
        reject_non_fqdn_hostname,
        reject_invalid_hostname,
        check_helo_access
                hash:/etc/postfix/helo_access,
        permit

Where helo_access looks like this:

domain.com            REJECT You do not belong to our domain

But, the last spam message I got claims to have a return path of info@xxxxxxxxxx and is addressed to sales@xxxxxxxxxx, a non-existent account. Why wasn't it dropped?

--
Mauricio                                raub-kudria-com
(if you need to email me, use this address =)
.