On Tue, Dec 23, 2025 at 10:31:48PM +0000, Mea Para via Postfix-users wrote:
> > postfix: fatal: config variable inet_interfaces: host not found: em0
>
> There are two problems with this.
>
> 1. ... Since the variable inet_interface is asking for a network
> interface name, ...
By design, per the documentation, and as implemented the above is not
correct. The "inet_interfaces" configuration parameter specifies the
**IP addresses** that a Postfix service should treat as its own.
It never was by design, documentation or implementation a list of the
interface names.
The first paragraph (read the rest too) of the documentation available
online at:
https://www.postfix.org/postconf.5.html#inet_interfaces
reads as follows:
The local network interface addresses that this mail system receives
mail on. Specify "all" to receive mail on all network interfaces
(default), "loopback-only" to receive mail on loopback network
interfaces only (Postfix version 2.2 and later), or zero or more
IPv4 or IPv6 addresses (IPv6 is supported in Postfix version 2.2 and
later). The parameter also controls whether Postfix will accept
mail for user@[ip.address], and prevents Postfix from delivering
mail to a host that has equal or larger MX pref‐ erence. Specify an
empty value if Postfix does not receive mail over the network, or if
all network listeners have an explicit IP address in master.cf.
> 2. If I supply an IP address, "postfix check" accepts it. However, an
> IP address is not a network interface, hence the check should fail.
No, because what determines the intended semantics of Postfix parameters
is their documentation, and not OCD fixation on what the parameter name
might naïvely suggest to a particular reader. :-(
> I understand that an IP address is what it has been taking for
> decades, but can we use the name of a network interface without
> incurring in this error?
No, because strings that are not IPv4 or IPv6 addresses have been, by
design, documentation, and now almost three decades of implementation,
interpreted as hostnames from which to obtain the desired IP addresses
indirectly (via getaddrinfo(3)).
--
Viktor. 🇺🇦 Слава Україні!
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