I have configured postfix on my server. telnet mydomain.com 25 helo validdomain.com mail from: [email protected] rcpt to: [email protected] data From: [email protected] To: [email protected] CC: [email protected],[email protected] Subject: Testing postfix Message body When I run this test, the email is delivered to valid user but also my server shoots an email to user1 and user2. I have implemented client, helo and recipient restrictions as below. How do I prevent the malicious use of CC as described here? Thank you Snap of main.cf ------------------- smtpd_client_restrictions = permit_mynetworks, reject_invalid_hostname, reject_rbl_client zen.spamhaus.org, reject_unknown_client, permit smtpd_helo_restrictions = permit_mynetworks, check_helo_access hash:/etc/postfix/helo_access, reject_unauth_pipelining, reject_non_fqdn_hostname, reject_invalid_hostname, warn_if_reject reject_unknown_hostname, permit smtpd_recipient_restrictions = reject_non_fqdn_sender, reject_non_fqdn_recipient, reject_non_fqdn_hostname, reject_invalid_hostname, permit_mynetworks, reject_unauth_pipelining, reject_unknown_sender_domain, reject_unknown_recipient_domain, reject_unauth_destination, reject_unknown_client, permit smtpd_sender_restrictions = permit_mynetworks, reject_non_fqdn_sender, reject_unknown_sender_domain, reject_unknown_address