Configure the interface binding via:
postconf -e "inet_interfaces = all
inet_interfaces (default: all)
The network interface addresses that this mail system receives mail on. Specify "all" to receive mail on all network
interfaces (default), and "loopback-only" to receive mail on loopback network interfaces only (Postfix version 2.2 and
later). The parameter also controls delivery of mail to user@[ip.address].
Note 1: you need to stop and start Postfix when this parameter changes.
Note 2: address information may be enclosed inside , but this form is not required here.
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. Support for IPv6 is available in Postfix version 2.2
On a multi-homed firewall with separate Postfix instances listening on the "inside" and "outside" interfaces, this can
prevent each instance from being able to reach remote SMTP servers on the "other side" of the firewall. Setting
smtp_bind_address to 0.0.0.0 avoids the potential problem for IPv4, and setting smtp_bind_address6 to :: solves the prob‐
lem for IPv6.
A better solution for multi-homed firewalls is to leave inet_interfaces at the default value and instead use explicit IP
addresses in the master.cf SMTP server definitions. This preserves the Postfix SMTP client's loop detection, by ensuring
that each side of the firewall knows that the other IP address is still the same host. Setting $inet_interfaces to a sin‐
gle IPv4 and/or IPV6 address is primarily useful with virtual hosting of domains on secondary IP addresses, when each IP
address serves a different domain (and has a different $myhostname setting).
See also the proxy_interfaces parameter, for network addresses that are forwarded to Postfix by way of a proxy or address
inet_interfaces = all (DEFAULT)
inet_interfaces = loopback-only (Postfix version 2.2 and later)
inet_interfaces = 127.0.0.1
inet_interfaces = 127.0.0.1, [::1] (Postfix version 2.2 and later)
inet_interfaces = 192.168.1.2, 127.0.0.1
postconf -e is an utility programm to maintain the postfix configuration.
-e Edit the main.cf configuration file, and update parameter set‐
tings with the "name=value" pairs on the postconf(1) command
line. The file is copied to a temporary file then renamed into
place. Specify quotes to protect special characters and white‐
space on the postconf(1) command line.
Any configuration changes needs to be recognized a restart of postfix.