Outgoing SMTP Authentication
Overview
When you need to route all outgoing mail through your ISP's MTA, and that MTA requires that you authenticate, certain settings in postfix are required.
For this example, we will use mailrelay.example.com as the outgoing relay The authentication user will be username The password will be password
Setting a relay host
Set the relay host in the admin console, MTA tab to point to your ISPs mta host.
Enabling smtp authentication
Run all these commands as the zimbra user
Create a text file mapping which name/password should be used for each given outbound destination:
echo mailrelay.example.com username:password > /opt/zimbra/conf/relay_password
Create a postfix lookup table
postmap /opt/zimbra/conf/relay_password
Test that the map is okay
postmap -q mailrelay.example.com /opt/zimbra/conf/relay_password
This should return username:password if done right
Make postfix use the above
postconf -e smtp_sasl_password_maps=hash:/opt/zimbra/conf/relay_password
Restart postfix:
postfix reload
Troubleshooting
After sending a test message, check the Log Files for the error
SASL authentication failure: No worthy mechs found
The fix for this is:
postconf -e smtp_sasl_security_options=
Nothing after the =
Restart postfix:
postfix reload