Postfix setup for Amazon SES on NixOS

configuration.nix

{ modulesPath, pkgs, ... }: {

  # AWS Defaults
  imports = [ "${modulesPath}/virtualisation/amazon-image.nix" ];
  ec2.hvm = true;

  # Server
  networking.hostName = "nixos-testing";
  boot.cleanTmpDir = true;

  # Applications
  environment.systemPackages = with pkgs; [
    mailutils
  ];

  # Mail
  services.postfix = {
    enable = true;
    # Using password and tls setup with postmap
    config = {
      smtp_sasl_auth_enable = "yes";
      smtp_sasl_security_options = "noanonymous";
      smtp_sasl_password_maps = "hash:/etc/postfix/saslpasswd";
      smtp_always_send_ehlo = "yes";
      smtp_use_tls = "yes";
      smtp_tls_security_level = "encrypt";
      smtp_tls_note_starttls_offer = "yes";
      smtp_tls_policy_maps = "hash:/etc/postfix/tls_policy";
    };
    relayHost = "email-smtp.us-east-1.amazonaws.com";
    relayPort = 587;
  };
}