could someone please give me step-by-step instructions on how to configure the fallback_relay option in Postfix?
I'm trying to set up a backup/secondary relayhost.
The instructions are somewhat confusing to me and I was hoping for some assistance.
Please see the details below:
fallback_relay (default: empty)
Optional list of relay hosts for SMTP destinations that can't be found or that are unreachable. With Postfix 2.3 this parameter is renamed to smtp_fallback_relay.
By default, mail is returned to the sender when a destination is not found, and delivery is deferred when a destination is unreachable.
The fallback relays must be SMTP destinations. Specify a domain, host, host
ort, [address] or [address]
ort; the form [host] turns off MX lookups. If you specify multiple SMTP destinations, Postfix will try them in the specified order.
Note: before Postfix 2.2, do not use the fallback_relay feature when relaying mail for a backup or primary MX domain. Mail would loop between the Postfix MX host and the fallback_relay host when the final destination is unavailable.
• In main.cf specify "relay_transport = relay",
• In master.cf specify "-o fallback_relay =" (i.e., empty) at the end of the relay entry.
• In transport maps, specify "relay:nexthop..." as the right-hand side for backup or primary MX domain entries.
Postfix version 2.2 and later will not use the fallback_relay feature for destinations that it is MX host for.
Any advice would be greatly appreciated.