Setup Guide =========== Mail servers can be a tricky thing to set up. This guide is supposed to run you through the most important steps to achieve a 10/10 score on ``mail-tester.com``. What you need: - A server with a public IP (referred to as ``server-IP``) - A Fully Qualified Domain Name (``FQDN``) where your server is reachable, so that other servers can find yours. Common FQDN include ``mx.example.com`` (where ``example.com`` is a domain you own) or ``mail.example.com``. The domain is referred to as ``server-domain`` (``example.com`` in the above example) and the ``FQDN`` is referred to by ``server-FQDN`` (``mx.example.com`` above). - A list of domains you want to your email server to serve. (Note that this does not have to include ``server-domain``, but may of course). These will be referred to as ``domains``. As an example, ``domains = [ example1.com, example2.com ]``. A) Setup server ~~~~~~~~~~~~~~~ The following describes a server setup that is fairly complete. Even though there are more possible options (see ``default.nix``), these should be the most common ones. .. code:: nix { config, pkgs, ... }: { imports = [ (builtins.fetchTarball { # Pick a commit from the branch you are interested in url = "https://gitlab.com/simple-nixos-mailserver/nixos-mailserver/-/archive/A-COMMIT-ID/nixos-mailserver-A-COMMIT-ID.tar.gz"; # And set its hash sha256 = "0000000000000000000000000000000000000000000000000000"; }) ]; mailserver = { enable = true; fqdn = ; domains = [ ]; # A list of all login accounts. To create the password hashes, use # nix run nixpkgs.apacheHttpd -c htpasswd -nbB "" "super secret password" | cut -d: -f2 loginAccounts = { "user1@example.com" = { hashedPassword = "$6$/z4n8AQl6K$kiOkBTWlZfBd7PvF5GsJ8PmPgdZsFGN1jPGZufxxr60PoR0oUsrvzm2oQiflyz5ir9fFJ.d/zKm/NgLXNUsNX/"; aliases = [ "postmaster@example.com" "postmaster@example2.com" ]; # Make this user the catchAll address for domains example.com and # example2.com catchAll = [ "example.com" "example2.com" ]; }; "user2@example.com" = { ... }; }; # Extra virtual aliases. These are email addresses that are forwarded to # loginAccounts addresses. extraVirtualAliases = { # address = forward address; "abuse@example.com" = "user1@example.com"; }; # Use Let's Encrypt certificates. Note that this needs to set up a stripped # down nginx and opens port 80. certificateScheme = 3; # Enable IMAP and POP3 enableImap = true; enablePop3 = true; enableImapSsl = true; enablePop3Ssl = true; # Enable the ManageSieve protocol enableManageSieve = true; # whether to scan inbound emails for viruses (note that this requires at least # 1 Gb RAM for the server. Without virus scanning 256 MB RAM should be plenty) virusScanning = false; }; } After a ``nixos-rebuild switch --upgrade`` your server should be good to go. If you want to use ``nixops`` to deploy the server, look in the subfolder ``nixops`` for some inspiration. If you're using `flakes `__, you can use the following minimal ``flake.nix`` as an example: .. code:: nix { description = "NixOS configuration"; inputs.simple-nixos-mailserver.url = "gitlab:simple-nixos-mailserver/nixos-mailserver"; outputs = { self, nixpkgs, simple-nixos-mailserver }: { nixosConfigurations = { hostname = nixpkgs.lib.nixosSystem { system = "x86_64-linux"; modules = [ simple-nixos-mailserver.nixosModule { mailserver = { enable = true; # ... }; } ]; }; }; }; } B) Setup everything else ~~~~~~~~~~~~~~~~~~~~~~~~ Step 1: Set DNS entry for server ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Add a DNS record to the domain ``server-domain`` with the following entries ================ ===== ==== ======== ============= Name (Subdomain) TTL Type Priority Value ================ ===== ==== ======== ============= ``server-FQDN`` 10800 A ``server-IP`` ================ ===== ==== ======== ============= This resolves DNS queries for ``server-FQDN`` to ``server-IP``. You can test if your setting is correct by :: ping Expected output: :: 64 bytes from (): icmp_seq=1 ttl=46 time=21.3 ms ... Note that it can take a while until a DNS entry is propagated. Step 2: Set rDNS (reverse DNS) entry for server ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Wherever you have rented your server, you should be able to set reverse DNS entries for the IP’s you own. Add an entry resolving ``server-IP`` to ``server-FQDN`` You can test if your setting is correct by :: host Expected output: :: .in-addr.arpa domain name pointer . Note that it can take a while until a DNS entry is propagated. Step 3: Set ``MX`` Records ^^^^^^^^^^^^^^^^^^^^^^^^^^ For every ``domain`` in ``domains`` do: \* Add a ``MX`` record to the domain ``domain`` :: | Name (Subdomain) | TTL | Type | Priority | Value | | ---------------- | ----- | ---- | -------- | ----------------- | | `domain` | | MX | 10 | `server-FQDN` | You can test this via :: dig -t MX Expected output: :: ... ;; ANSWER SECTION: 10800 IN MX 10 ... Note that it can take a while until a DNS entry is propagated. Step 4: Set ``SPF`` Records ^^^^^^^^^^^^^^^^^^^^^^^^^^^ For every ``domain`` in ``domains`` do: \* Add a ``SPF`` record to the domain ``domain`` :: | Name (Subdomain) | TTL | Type | Priority | Value | | ---------------- | ----- | ---- | -------- | ----------------- | | `domain` | 10800 | TXT | | `v=spf1 ip4: -all` | You can check this with ``dig -t TXT `` similar to the last section. Note that ``SPF`` records are set as ``TXT`` records since RFC1035. Note that it can take a while until a DNS entry is propagated. If you want to use multiple servers for your email handling, don’t forget to add all server IP’s to this list. Step 5: Set ``DKIM`` signature ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ In this section we assume that your ``dkimSelector`` is set to ``mail``. If you have a different selector, replace all ``mail``\ ’s below accordingly. For every ``domain`` in ``domains`` do: \* Go to your server and navigate to the dkim key directory (by default ``/var/dkim``). There you will find a public key for any domain in the ``domain.txt`` file. It will look like ``mail._domainkey IN TXT "v=DKIM1; r=postmaster; g=*; k=rsa; p=" ; ----- DKIM mail for domain.tld`` \* Add a ``DKIM`` record to the domain ``domain`` :: | Name (Subdomain) | TTL | Type | Priority | Value | | ---------------- | ----- | ---- | -------- | ----------------- | | mail._domainkey.`domain` | 10800 | TXT | | `v=DKIM1; p=` | You can check this with ``dig -t TXT mail._domainkey.`` similar to the last section. Note that it can take a while until a DNS entry is propagated. Step 6: Set ``DMARC`` record ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ For every ``domain`` in ``domains`` do: - Add a ``DMARC`` record to the domain ``domain`` ==================== ===== ==== ======== ==================== Name (Subdomain) TTL Type Priority Value ==================== ===== ==== ======== ==================== \_dmarc.\ ``domain`` 10800 TXT ``v=DMARC1; p=none`` ==================== ===== ==== ======== ==================== You can check this with ``dig -t TXT _dmarc.`` similar to the last section. Note that it can take a while until a DNS entry is propagated. C) Test your Setup ~~~~~~~~~~~~~~~~~~ Write an email to your aunt (who has been waiting for your reply far too long), and sign up for some of the finest newsletters the Internet has. Maybe you want to sign up for the `SNM Announcement List `__? Besides that, you can send an email to `mail-tester.com `__ and see how you score, and let `mxtoolbox.com `__ take a look at your setup, but if you followed the steps closely then everything should be awesome!