Question: When specifying 2 or more address for the
inet_interfaces directive, will postfix still bind outgoing mail to one of them?
The postfix docs state:
When inet_interfaces specifies just one IPv4 and/or IPv6 address that is not a loopback address, the Postfix SMTP client will use this address as the IP source address for outbound mail.
Due to the need for a loopback address I need to be able to bind to either 127.0.0.1 or my WAN address depending on mail destination. My current setting is:
inet_interfaces = 126.96.36.199, [2600:1234::1234:5678:abcd:abcd], 127.0.0.1
Previously I had used
smtp_bind_address6 but was causing problems since postfix needs to access loopback for local mail delivery.
Also, I do in fact have 5 static IPv4 addresses for this server, hence the desire to only use one of them. Since the docs state
just one IPv4 and/or IPv6 I'm unsure whether specifying all three will ensure that outgoing mail is bound to anything at all.