Change:
<ins> { config, lib, pkgs, ... }: with lib; let name = "maddy"; cfg = config.services.maddy; defaultConfig = '' tls off auth.pass_table local_authdb { table sql_table { driver sqlite3 dsn credentials.db table_name passwords } } storage.imapsql local_mailboxes { driver sqlite3 dsn imapsql.db } table.chain local_rewrites { optional_step regexp "(.+)+(.+)@(.+)" "$1@$3" optional_step static { entry postmaster postmaster@$(primary_domain) } optional_step file /etc/maddy/aliases } msgpipeline local_routing { destination postmaster $(local_domains) { modify { replace_rcpt &local_rewrites } deliver_to &local_mailboxes } default_destination { reject 550 5.1.1 "User doesn't exist" } } smtp tcp://0.0.0.0:25 { limits { all rate 20 1s all concurrency 10 } dmarc yes check { require_mx_record dkim spf } source $(local_domains) { reject 501 5.1.8 "Use Submission for outgoing SMTP" } default_source { destination postmaster $(local_domains) { deliver_to &local_routing } default_destination { reject 550 5.1.1 "User doesn't exist" } } } submission tcp://0.0.0.0:587 { limits { all rate 50 1s } auth &local_authdb source $(local_domains) { check { authorize_sender { prepare_email &local_rewrites user_to_email identity } } destination postmaster $(local_domains) { deliver_to &local_routing } default_destination { modify { dkim $(primary_domain) $(local_domains) default } deliver_to &remote_queue } } default_source { reject 501 5.1.8 "Non-local sender domain" } } target.remote outbound_delivery { limits { destination rate 20 1s destination concurrency 10 } mx_auth { dane mtasts { cache fs fs_dir mtasts_cache/ } local_policy { min_tls_level encrypted min_mx_level none } } } target.queue remote_queue { target &outbound_delivery autogenerated_msg_domain $(primary_domain) bounce { destination postmaster $(local_domains) { deliver_to &local_routing } default_destination { reject 550 5.0.0 "Refusing to send DSNs to non-local addresses" } } } imap tcp://0.0.0.0:143 { auth &local_authdb storage &local_mailboxes } ''; in { options = { services.maddy = { enable = mkEnableOption "Maddy, a free an open source mail server"; user = mkOption { default = "maddy"; type = with types; uniq string; description = '' Name of the user under which maddy will run. If not specified, a default user will be created. ''; }; group = mkOption { default = "maddy"; type = with types; uniq string; description = '' Name of the group under which maddy will run. If not specified, a default group will be created. ''; }; hostname = mkOption { default = "localhost"; type = with types; uniq string; example = ''example.com''; description = '' Hostname to use. It should be FQDN. ''; }; primaryDomain = mkOption { default = "localhost"; type = with types; uniq string; example = ''mail.example.com''; description = '' Primary MX domain to use. It should be FQDN. ''; }; localDomains = mkOption { type = with types; listOf str; default = ["$(primary_domain)"]; example = [ "$(primary_domain)" "example.com" "other.example.com" ]; description = '' Define list of allowed domains. ''; }; config = mkOption { type = with types; nullOr lines; default = defaultConfig; description = '' Server configuration. ''; }; openFirewall = mkOption { type = types.bool; default = false; description = '' Open the configured incoming and outgoing mail server ports. ''; }; }; }; config = mkIf cfg.enable { systemd = { packages = [ pkgs.maddy ]; services.maddy = { serviceConfig = { User = "${cfg.user}"; Group = "${cfg.group}"; }; wantedBy = [ "multi-user.target" ]; }; }; environment.etc."maddy/maddy.conf" = { text = '' $(hostname) = ${cfg.hostname} $(primary_domain) = ${cfg.primaryDomain} $(local_domains) = ${toString cfg.localDomains} hostname ${cfg.hostname} ${cfg.config} ''; }; users.users = optionalAttrs (cfg.user == "maddy") { maddy = { description = "Maddy service user"; group = cfg.group; home = "/var/lib/maddy"; createHome = true; isSystemUser = true; }; }; users.groups = mkIf (cfg.group == "maddy") { maddy = pkgs.lib.mkForce { name = cfg.group; }; }; networking.firewall = mkIf cfg.openFirewall { allowedTCPPorts = [ 25 143 587 ]; }; environment.systemPackages = [ pkgs.maddy ]; }; } </ins>

Discussion:
Maddy, a small and compact mail server written in Go, was merged as a package with by . Having a NixOS module to enable and configure it would be really great! If someone is interested in creating a PR, I will be happy to help and test it :+1: Best regards Jonas
Hi, I dont have any sort of way to properly test this within the actual nixos repo but I've got a personal working module/service you can try
I did something very similar to the above, but based my serviceConfig on the example . It contains quite a bit more of the systemd security features, so if you want to make something to include in nixpkgs I think all these things should be on! I also hooked it up to Dovecot, hence the waiting script, not sure if that's the best way of doing it.
How about this: Nice and simple.
Have you tried this? Somehow it doesn't work for me:
- it looks like the units aren't included in the nixpkgs package :man_shrugging:, but I created a PR to fix this in Please review, test, and approve PR. I have never used so I wouldn't want to merge that PR without you (or someone else) testing. Thanks!