228 lines
7.1 KiB
ReStructuredText
228 lines
7.1 KiB
ReStructuredText
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
|
||
`<https://mail-tester.com>`_.
|
||
|
||
What you need is:
|
||
|
||
- a server running NixOS with a public IP
|
||
- a domain name.
|
||
|
||
.. note::
|
||
|
||
In the following, we consider a server with the public IP ``1.2.3.4``
|
||
and the domain ``example.com``.
|
||
|
||
First, we will set the minimum DNS configuration to be able to deploy
|
||
an up and running mail server. Once the server is deployed, we could
|
||
then set all DNS entries required to send and receive mails on this
|
||
server.
|
||
|
||
Setup DNS A record for server
|
||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||
|
||
Add a DNS record to the domain ``example.com`` with the following
|
||
entries
|
||
|
||
==================== ===== ==== =============
|
||
Name (Subdomain) TTL Type Value
|
||
==================== ===== ==== =============
|
||
``mail.example.com`` 10800 A ``1.2.3.4``
|
||
==================== ===== ==== =============
|
||
|
||
You can check this with
|
||
|
||
::
|
||
|
||
$ ping mail.example.com
|
||
64 bytes from mail.example.com (1.2.3.4): icmp_seq=1 ttl=46 time=21.3 ms
|
||
...
|
||
|
||
Note that it can take a while until a DNS entry is propagated. This
|
||
DNS entry is required for the Let's Encrypt certificate generation
|
||
(which is used in the below configuration example).
|
||
|
||
Setup the server
|
||
~~~~~~~~~~~~~~~~
|
||
|
||
The following describes a server setup that is fairly complete. Even
|
||
though there are more possible options (see the `NixOS Mailserver
|
||
options documentation <options.html>`_), these should be the most
|
||
common ones.
|
||
|
||
.. code:: nix
|
||
|
||
{ config, pkgs, ... }: {
|
||
imports = [
|
||
(builtins.fetchTarball {
|
||
# Pick a release version you are interested in and set its hash, e.g.
|
||
url = "https://gitlab.com/simple-nixos-mailserver/nixos-mailserver/-/archive/nixos-23.05/nixos-mailserver-nixos-23.05.tar.gz";
|
||
# To get the sha256 of the nixos-mailserver tarball, we can use the nix-prefetch-url command:
|
||
# release="nixos-23.05"; nix-prefetch-url "https://gitlab.com/simple-nixos-mailserver/nixos-mailserver/-/archive/${release}/nixos-mailserver-${release}.tar.gz" --unpack
|
||
sha256 = "0000000000000000000000000000000000000000000000000000";
|
||
})
|
||
];
|
||
|
||
mailserver = {
|
||
enable = true;
|
||
fqdn = "mail.example.com";
|
||
domains = [ "example.com" ];
|
||
|
||
# A list of all login accounts. To create the password hashes, use
|
||
# nix-shell -p mkpasswd --run 'mkpasswd -sm bcrypt'
|
||
loginAccounts = {
|
||
"user1@example.com" = {
|
||
hashedPasswordFile = "/a/file/containing/a/hashed/password";
|
||
aliases = ["postmaster@example.com"];
|
||
};
|
||
"user2@example.com" = { ... };
|
||
};
|
||
|
||
# Use Let's Encrypt certificates. Note that this needs to set up a stripped
|
||
# down nginx and opens port 80.
|
||
certificateScheme = "acme-nginx";
|
||
};
|
||
security.acme.acceptTerms = true;
|
||
security.acme.defaults.email = "security@example.com";
|
||
}
|
||
|
||
After a ``nixos-rebuild switch`` your server should be running all
|
||
mail components.
|
||
|
||
Setup all other DNS requirements
|
||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||
|
||
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 ``1.2.3.4``
|
||
to ``mail.example.com``.
|
||
|
||
.. warning::
|
||
|
||
We don't recommend setting up a mail server if you are not able to
|
||
set a reverse DNS on your public IP because sent emails would be
|
||
mostly marked as spam. Note that many residential ISP providers
|
||
don't allow you to set a reverse DNS entry.
|
||
|
||
You can check this with
|
||
|
||
::
|
||
|
||
$ nix-shell -p bind --command "host 1.2.3.4"
|
||
4.3.2.1.in-addr.arpa domain name pointer mail.example.com.
|
||
|
||
Note that it can take a while until a DNS entry is propagated.
|
||
|
||
Set a ``MX`` record
|
||
^^^^^^^^^^^^^^^^^^^
|
||
|
||
|
||
Add a ``MX`` record to the domain ``example.com``.
|
||
|
||
================ ==== ======== =================
|
||
Name (Subdomain) Type Priority Value
|
||
================ ==== ======== =================
|
||
example.com MX 10 mail.example.com
|
||
================ ==== ======== =================
|
||
|
||
You can check this with
|
||
|
||
::
|
||
|
||
$ nix-shell -p bind --command "host -t mx example.com"
|
||
example.com mail is handled by 10 mail.example.com.
|
||
|
||
Note that it can take a while until a DNS entry is propagated.
|
||
|
||
Set a ``SPF`` record
|
||
^^^^^^^^^^^^^^^^^^^^
|
||
|
||
Add a `SPF <https://en.wikipedia.org/wiki/Sender_Policy_Framework>`_
|
||
record to the domain ``example.com``.
|
||
|
||
================ ===== ==== ================================
|
||
Name (Subdomain) TTL Type Value
|
||
================ ===== ==== ================================
|
||
example.com 10800 TXT `v=spf1 a:mail.example.com -all`
|
||
================ ===== ==== ================================
|
||
|
||
You can check this with
|
||
|
||
::
|
||
|
||
$ nix-shell -p bind --command "host -t TXT example.com"
|
||
example.com descriptive text "v=spf1 a:mail.example.com -all"
|
||
|
||
Note that it can take a while until a DNS entry is propagated.
|
||
|
||
Set ``DKIM`` signature
|
||
^^^^^^^^^^^^^^^^^^^^^^
|
||
|
||
On your server, the ``opendkim`` systemd service generated a file
|
||
containing your DKIM public key in the file
|
||
``/var/dkim/example.com.mail.txt``. The content of this file looks
|
||
like
|
||
|
||
::
|
||
|
||
mail._domainkey IN TXT "v=DKIM1; k=rsa; s=email; p=<really-long-key>" ; ----- DKIM mail for domain.tld
|
||
|
||
where ``really-long-key`` is your public key.
|
||
|
||
Based on the content of this file, we can add a ``DKIM`` record to the
|
||
domain ``example.com``.
|
||
|
||
=========================== ===== ==== ==============================
|
||
Name (Subdomain) TTL Type Value
|
||
=========================== ===== ==== ==============================
|
||
mail._domainkey.example.com 10800 TXT ``v=DKIM1; p=<really-long-key>``
|
||
=========================== ===== ==== ==============================
|
||
|
||
You can check this with
|
||
|
||
::
|
||
|
||
$ nix-shell -p bind --command "host -t txt mail._domainkey.example.com"
|
||
mail._domainkey.example.com descriptive text "v=DKIM1;p=<really-long-key>"
|
||
|
||
Note that it can take a while until a DNS entry is propagated.
|
||
|
||
Set a ``DMARC`` record
|
||
^^^^^^^^^^^^^^^^^^^^^^
|
||
|
||
Add a ``DMARC`` record to the domain ``example.com``.
|
||
|
||
======================== ===== ==== ====================
|
||
Name (Subdomain) TTL Type Value
|
||
======================== ===== ==== ====================
|
||
_dmarc.example.com 10800 TXT ``v=DMARC1; p=none``
|
||
======================== ===== ==== ====================
|
||
|
||
You can check this with
|
||
|
||
::
|
||
|
||
$ nix-shell -p bind --command "host -t TXT _dmarc.example.com"
|
||
_dmarc.example.com descriptive text "v=DMARC1; p=none"
|
||
|
||
Note that it can take a while until a DNS entry is propagated.
|
||
|
||
|
||
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 <https://www.freelists.org/list/snm>`__?
|
||
|
||
Besides that, you can send an email to
|
||
`mail-tester.com <https://www.mail-tester.com/>`__ and see how you
|
||
score, and let `mxtoolbox.com <http://mxtoolbox.com/>`__ take a look at
|
||
your setup, but if you followed the steps closely then everything should
|
||
be awesome!
|