First apologize me for the grammar, english isn't my native language. The problem I have is users from our local zimbra mail are getting spam messages from other email addresses who don't exist, like annymous172167@ourdomain
I found that the problem can be OpenRelay in postfix configuration. I did this test http://www.tech-recipes.com/rx/381/send_mail_via_telnet_test_for_open_relay/ and found that I can send emails via telnet without any authentication. To resolve the problem, I tried to change the postfix configuration.
My original conf file (/opt/zimbra/postfix-184.108.40.206z/conf/main.cf) was
smtpd_sender_restrictions = check_sender_access regexp:/opt/zimbra/postfix/conf/tag_as_originating.re, permit_mynetworks, permit_sasl_authenticated, permit_tls_clientcerts, check_sender_access regexp:/opt/zimbra/postfix/conf/tag_as_foreign.re, check_sender_access hash:/opt/zimbra/postfix/conf/access_table
And I tried to change to:
smtpd_sender_restrictions = reject_unknown_sender_domain
But when I run
$postfix reload the configuration come back to the original one, without any changes.