Saturday, May 2, 2026

Today I have been playing during 2 hours with 7 postfix config parameters (myhostname, myorigin, mydestination, inet_protocols, inet_interfaces, local_transport and smtp_bind_address) on two servers (kuu and lumi). There were moments when I didn’t understand the world and had the feeling that some hidden random error generator is running somewhere…

It seems that the article How to Configure Postfix as a Send-Only SMTP Server on IPv4 is not what we want. A default postfix config is good for us, I just need to set three parameters correctly: myhostname, mydestination and myorigin.

TIL:

  • postconf key1 key2 shows the current settings, one line key=value for each specified key.

  • postconf key=value updates the main.cf file from the command line. This is useful when playing around. You can specify multiple key=value pairs. A value can be empty. Know your bash rules.

  • systemctl restart is more than systemctl reload. When you change inet_interfaces or inet_protocols, reloading won’t do it and postfix even issues a warning… but only in the system journal, not on the command line.

  • Saying “echo foo | mail -s test root” is not enough. It’s important to specify -r (or --return-address) because mail does not consult /etc/mailname, it will just say username@hostname, and hostname is just our nickname, and most mail servers refuse emails with a non-existing domain name in the From field. Here is a generic command-line for sending a test email:

    $ echo foo | mail -r `whoami`@`cat /etc/mailname` -s test root

    (I wonder whether it would be better to set hostname to the the full public name. I set it to the nickname only because I don’t want to see the full public name in the prompt.)

  • In Postfix you can say “/etc/mailname” as the value for myorigin, but not for myhostname. Seems that Postfix checks for a “/” at the beginning only for myorigin. Don’t ask me why.

Here is my recipe for configuring:

# postconf myhostname=`cat /etc/mailname`
# postconf myorigin=/etc/mailname
# postconf 'mydestination=$myhostname,localhost'
# systemctl restart postfix

To verify these three parameters:

# postconf myhostname mydestination myorigin
myhostname = lumi.mylino.net
mydestination = $myhostname,localhost
myorigin = /etc/mailname