On Sat, Jun 18, 2022 at 06:44:55PM -0600, James Feeney wrote: > Running postfix on Linux in a Network Namespace, and then running > postfix sendmail from "outside" that Network Namespace, gives an > error: > > postfix/sendmail[606899]: fatal: parameter inet_interfaces: no local > interface found for <network_namespace_interface_IP_address>
The common Postfix initialisation code that consumes main.cf and sets the core parameter values also initialises "inet_interfaces". Sure, sendmail does not generally do much with this setting, but you could then set "inet_interfaces = loopback-only" if nothing else suitable is available. > Obviously postfix sendmail is communicating with postfix running in > the network namespace, but why is postfix sendmail then looking for an > IP interface address "inside" the network namespace, instead of simply > passing the message to postdrop, as shown in the diagram? The sendmail(1) program runs into the issue while performing basic common initialisation that, includes among other things, setting up inet_interfaces. > Is postfix sendmail actually running over network layer 3 IP? No. It is mostly just a wrapper around postdrop(1). Though its emulation of some other Sendmail features includes - Starting postfix: "sendmail -bd" or "sendmail -bl" - Receving SMTP messages: "sendmail -bs" The first is implemented by executing "postfix start", so there's no network use directly in sendmail(1) itself. The second is implemented by executing "smtpd -S", so again there's no network use directly in sendmail(1). -- Viktor.