Smtp fallback relay

In the event your zimbraMtaRelayHost MTA becomes, unreachable, you can configure Zimbra's MTA to fallback on other MTA machine that can relay messages.

For example:

zmprov gs `zmhostname` | grep zimbraMtaRelayHost
zimbraMtaRelayHost: mta1.domain.com

To add additional MTA's:

postconf -e smtp_fallback_relay="mta2.domain.com:25, mta3.domain.com:25" 

zmmtactl restart

If mta1 was unreachable, mta2 and mta3 can be used as backup.

If you want the change to survive upgrades:

1) Add the following to the /opt/zimbra/conf/zmmta.cf file

POSTCONF smtp_fallback_relay            LOCAL postfix_smtp_fallback_relay

***I would suggest adding the line underneath "POSTCONF inet_protocols   VAR zimbraPostconfProtocol***

2) Add the setting to the localconfig

zmlocalconfig -e postfix_smtp_fallback_relay="mta2.domain.com:25, mta3.domain.com:25"