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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-2.10.3.2z/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.

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