Authen
| postmap /opt/zimbra/conf/relay_password |
| smtp.mailgun.org username:password |
Backup file /opt/zimbra/postfix/conf/main.cf
| zmlocalconfig -e postfix_smtp_sasl_security_options=noanonymous |
| zmlocalconfig -e postfix_smtp_sasl_auth_enable=yes |
| zmlocalconfig -e postfix_smtp_sasl_password_maps=hash:/opt/zimbra/conf/relay_password |
| zmlocalconfig -e postfix_smtp_tls_security_level=may |
| zmlocalconfig -e postfix_smtp_cname_overrides_servername=no |
#zmprov ms zmhostname zimbraMtaRelayHost smtp.relay.org |
Sender Relay.
| relay-perdomain | zmprov ms zmhostname zimbraMtaRelayHost '' |
| zmlocalconfig -e postfix_sender_dependent_relayhost_maps=hash:/opt/zimbra/postfix/conf/bysender | |
| postmap /opt/zimbra/postfix/conf/bysender | |
| @mydomain.com [smtp.relay.org] |