For anyone encountering this error, I've traced it to a regression of a very old bug relating to systemd service ordering dependencies.
In my case, OS is CentOS Linux release 8.4.2105 postfix-3.5.8-1.el8.x86_64 Since a recent update I've found that, after every reboot, Postfix fails to start, and logs the message fatal: parameter inet_interfaces: no local interface found for 127.0.0.2 If I then manually start Postfix (systemctl start postfix) it starts right up with no complaints. Long story short, this appears to be a regression of the 6-year-old systemd problem documented at https://bugs.launchpad.net/ubuntu/+source/postfix/+bug/1519331 The problem is that in CentOS 8, a recent update seems to have changed Postfix's systemd service dependency from After=syslog.target network-online.target to After=syslog.target network.target This means that Postfix now starts up before the network is completely up, and systemd's DNS resolution hack (systemd-resolved.service), finding no interfaces up yet, resolves 'localhost' to 127.0.0.2. (man systemd-resolved.service) The simple fix is to create an override file with systemctl edit postfix.service" and restore the "After=" dependency on network-online.target -- Jim Garrison j...@acm.org
