NixOS-SMTPRelay

This repository contains .nix files to set up a SMTP-Relay using Postfix on the server-side as add-on to the NixOS-Mailserver and msmtp as SMTP client.

You can use this to route emails through your email server from a client without a static public IP address to avoid blacklisting or to not set up an entire email server within your application.

• Clone this repo with git clone https://github.com/DieSchoeneWolke/NixOS-SMTPRelay.git on your client.

• Write your credentials with sudo mkdir -p /etc/.secrets/ && sudo nano /etc/.secrets/smtp_password.txt to be used by msmtp.

• Write your credentials and domain in the relay.nix file with nano ./NixOS-STMPRelay/relay.nix to be used by Postfix at the NixOS-Mailserver.

• Transfer the file to your NixOS-Mailserver server at /etc/nixos/relay.nix and append it to your configuration.nix with sudo nano /etc/nixos/configuration.nix

{ config, pkgs, ... }: {
  imports = [
    ./hardware-configuration.nix
    ./relay.nix
  ];

• Build a new generation with sudo nixos-rebuild switch on both machines.

• Send a test email with echo -e "Content-Type: text/plain\r\nSubject: Test\r\n\r\nHello World" | sudo sendmail <Email address> from your client.

⚠ This is not a best practice solution. You should secure the credentials using sops-nix or any other secret management solution.