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