Stable Releases

• SNM v2.0.2

Latest Release (Candidate)

Features

v2.0

• Continous Integration Testing
• Multiple Domains
• Postfix MTA
  • smtp on port 25
  • submission port 587
  • lmtp with dovecot
• Dovecot
  • maildir folders
  • imap starttls on port 143
  • pop3 starttls on port 110
• Certificates
  • manual certificates
  • on the fly creation
  • Let's Encrypt
• Spam Filtering
  • via rspamd
• Virus Scanning
  • via clamav
• DKIM Signing
  • via opendkim
• User Management
  • declarative user management
  • declarative password management
• Sieves
  • A simple standard script that moves spam
  • Allow user defined sieve scripts

In the future

• User Aliases
  • More complete alias support (Differentiate between forwarding addresses and sending aliases)
• DKIM Signing
  • Allow a per domain selector

Changelog

v1.0 -> v1.1

• Changed structure to Nix Modules
• Adds Sieve support

v1.1 -> v2.0

• rename domain to fqdn, seperate fqdn from domains
• multi domain support

Quick Start

{ config, pkgs, ... }:
{
  imports = [
    (builtins.fetchTarball "https://github.com/r-raymond/nixos-mailserver/archive/v2.0.2.tar.gz")
  ];

  mailserver = {
    enable = true;
    fqdn = "mail.example.com";
    domains = [ "example.com" "example2.com" ];
    loginAccounts = {
        "user1@example.com" = {
            hashedPassword = "$6$/z4n8AQl6K$kiOkBTWlZfBd7PvF5GsJ8PmPgdZsFGN1jPGZufxxr60PoR0oUsrvzm2oQiflyz5ir9fFJ.d/zKm/NgLXNUsNX/";

            aliases = [
                "info@example.com"
                "postmaster@example.com"
                "postmaster@example2.com"
            ];
        };
    };
  };
}

For a complete list of options, see default.nix.

How to Set Up a 10/10 Mail Server 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. Note 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.

{ config, pkgs, ... }:
{
  imports = [
    (builtins.fetchTarball "https://github.com/r-raymond/nixos-mailserver/archive/v2.0.2.tar.gz")
  ];

  mailserver = {
    enable = true;
    fqdn = <server-FQDN>;
    domains = [ <domains> ];

    # A list of all login accounts. To create the password hashes, use
    # mkpasswd -m sha-512 "super secret password"
    loginAccounts = {
        "user1@example.com" = {
            hashedPassword = "$6$/z4n8AQl6K$kiOkBTWlZfBd7PvF5GsJ8PmPgdZsFGN1jPGZufxxr60PoR0oUsrvzm2oQiflyz5ir9fFJ.d/zKm/NgLXNUsNX/";

            aliases = [
                "postmaster@example.com"
                "postmaster@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;

    # 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.

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 resolved DNS equries for server-FQDN to server-IP. You can test if your setting is correct by

ping <server-FQDN>
64 bytes from <server-FQDN> (<server-IP>): 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 <server-IP>
<server-IP>.in-addr.arpa domain name pointer <server-FQDN>.

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 <domain>

...
;; ANSWER SECTION:
<domain>    10800   IN  MX  10 <server-FQDN>
...

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:<server-IP> -all

You can check this with dig -t TXT <domain> similar to the last section.

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

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=<really-long-key>" ; ----- 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=<really-long-key>

You can check this with dig -t TXT <domain> 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.

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!

How to Backup

This is really easy. First off you should have a backup of your configuration.nix file where you have the server config (but that is already in a git repository right?)

Next you need to backup /var/vmail or whatever you have specified for the option mailDirectory. This is where all the mails reside. Good options are a cron job with rsync or scp. But really anything works, as it is simply a folder with plenty of files in it. If your backup solution does not preserve the owner of the files don't forget to chown them to virtualMail:virtualMail if you copy them back (or whatever you specified as vmailUserName, and vmailGoupName).

Finally you can (optionally) make a backup of /var/dkim (or whatever you specified as dkimKeyDirectory). If you should lose those don't worry, new ones will be created on the fly. But you will need to repeat step B)5 and correct all the dkim keys.

How to Test for Development

You can test the setup via nixops. After installation, do

nixops create nixops/single-server.nix nixops/vbox.nix -d mail
nixops deploy -d mail
nixops info -d mail

You can then test the server via e.g. telnet. To log into it, use

nixops ssh -d mail mailserver

To test imap manually use

openssl s_client -host mail.example.com -port 143 -starttls imap

A Complete Mail Server Without Moving Parts

Used Technologies

• Nixos
• Nixpkgs
• Dovecot
• Postfix
• Rmilter
• Rspamd
• Clamav
• Opendkim
• Pam

Features

• unlimited domain
• unlimited mail accounts
• unlimited aliases for every mail account
• spam and virus checking
• dkim signing of outgoing emails
• imap (optionally pop3)
• startTLS

Nonfeatures

• moving parts
• SQL databases
• configurations that need to be made after nixos-rebuild switch
• complicated storage schemes
• webclients / http-servers

Contributors

• Special thanks to @Infinisil for the module rewrite
• Special thanks to @jbboehr for multidomain implementation
• @danbst
• @phdoerfler
• @eqyiel

Alternative Implementations

• NixCloud Webservices

Credits

• send mail graphic by tnp_dreamingmao from TheNounProject is licensed under CC BY 3.0
• Logo made with Logomakr.com