Mail stub

The mailstub role provides a minimal Postfix which is mostly usable to locally collect and queue mails to hand them off to another mail server for actual delivery (relay). Sending email directly will not work well due to spam protection measures on the receiving side. Notably the mail stub does not configure DKIM signing – use Mail server.

Configuring Postfix is possible in NixOS configuration in the services.postfix module.

Configuring as relay

This is an example configuration to collect mails locally and send them all to smtp.example.com:

services.postfix.settings.main = {
  relayhost = [
    "[smtp.example.com]:587"
  ];
  smtp_sasl_auth_enable = true;
  smtp_sasl_password_maps = "hash:/etc/local/postfix/sasl_passwd";
  smtp_sasl_security_options = "noanonymous";
  smtp_use_tls = true;
};

/etc/local/postfix/sasl_passwd

[smtp.example.com]:587 smtp_username:smtp_password

Run in /etc/local/postfix

postmap sasl_passwd

Run sudo fc-manage switch to activate.