Postfix PCI Compliance in ZCS
Reconfigure the Postfix SSL/TLS settings
1. Make a backup of /opt/zimbra/postfix/conf/main.cf in case you need to rollback or refer to after an upgrade.
2. Log in as root in the command line utility. Switch to the zimbra user account.
su - zimbra
3. Type the following commands:
postconf -e smtpd_tls_mandatory_protocols="SSLv3, TLSv1" postconf -e smtpd_tls_mandatory_ciphers="high" postconf -e smtpd_tls_exclude_ciphers="aNULL, MD5"
The SSL/TLS settings are now reconfigured. The changes will take effect immediately.
4. To ensure that your changes are not overwritten by a future Zimbra upgrade, you can set them in the local config.
zmlocalconfig -e smtpd_tls_mandatory_protocols="SSLv3, TLSv1" zmlocalconfig -e smtpd_tls_mandatory_ciphers="high" zmlocalconfig -e smtpd_tls_exclude_ciphers="aNULL, MD5"
Reference - http://www.postfix.org/TLS_README.html