maddy/docs/tutorials/setting-up.md

Installation & initial configuration

This is the practical guide on how to set up a mail server using maddy for personal use. It omits most of the technical details for brevity and just gives you the minimal list of things you need to be aware of and what to do to make stuff work.

For purposes of clarity, these values are used in this tutorial as examples, wherever you see them, you need to replace them with your actual values:

• Domain: example.org
• MX domain (hostname): mx.example.org
• IPv4 address: 10.2.3.4
• IPv6 address: 2001:beef::1

Getting a server

Where to get a server to run maddy on is out of the scope of this article. Any VPS (virtual private server) will work fine for small configurations. However, there are a few things to keep in mind:

• Make sure your provider does not block SMTP traffic (25 TCP port). Most VPS providers don't do it, but some "cloud" providers (such as Google Cloud) do it, so you can't host your mail there.
• ...

Installing maddy

Since there are currently no pre-compiled binaries for maddy, we are going to build it from the source. Nothing scary, this is relatively easy to do with Go.

One dependency you need to figure out is the C compiler, it is needed for SQLite3 support which is used in the default configuration. On Debian-based distributions, this should be enough:

# apt-get install build-essential

build.sh script will do the rest for you:

$ curl 'https://foxcpp.dev/maddy/build.sh' | bash

Note: If you can't / don't use this script for some reason, instructions for manual installation can be found here

Host name + domain

Open /etc/maddy/maddy.conf with vimyour favorite editor and change the following lines to match your server name and domain you want to handle mail for.

$(hostname) = mx.example.org
$(primary_domain) = example.org

TLS certificates

One thing that can't be automagically configured is TLS certs. If you already have them somewhere - use them, open /etc/maddy/maddy.conf and put the right paths in. You need to make sure maddy can read them while running as unprivileged user (maddy never runs as root, even during start-up), one way to do so is to use ACLs (replace with your actual paths):

$ sudo setfacl -R -m u:maddy:rX /etc/ssl/example.org.crt /etc/ssl/example.org.key

Let's Encrypt and certbot

If you use certbot to manage your certificates, you can simply symlink /etc/maddy/certs into /etc/letsencrypt/live. maddy will pick the right certificate depending on the domain you specified during installation.

You still need to make keys readable for maddy, though:

$ sudo setfacl -R -m u:maddy:rX /etc/letsencrypt/{live,archive}

maddy reloads TLS certificates from disk once in a minute so it will notice renewal. It is possible to force reload via systemctl reload maddy (or just killall -USR2 maddy).

First run

systemctl start maddy

Well, it should be running now, except that it is useless because we haven't configured DNS records.

DNS records

How it is configured depends on your DNS provider (or server, if you run your own). Here is how your DNS zone should look like:

; Basic domain->IP records, you probably already have them.
example.org.   A     10.2.3.4
example.org.   AAAA  2001:beef::1

; It says that "server example.org is handling messages for example.org".
example.org.   MX    10 example.org.

; Use SPF to say that the servers in "MX" above are allowed to send email
; for this domain, and nobody else.
example.org.   TXT   "v=spf1 mx -all"

; Opt-in into DMARC with permissive policy and request reports about broken
; messages.
_dmarc.example.org.   TXT    "v=DMARC1; p=none; ruf=postmaster@example.org"

And the last one, DKIM key, is a bit tricky. maddy generated a key for you on the first start-up. You can find it in /var/lib/maddy/dkim_keys/example.org_default.dns. You need to put it in a TXT record for default._domainkey.example.org domain, like that:

default._domainkey.example.org    TXT   "v=DKIM1; k=ed25519; p=nAcUUozPlhc4VPhp7hZl+owES7j7OlEv0laaDEDBAqg="

MTA-STS

By default SMTP is not protected against active attacks. MTA-STS policy tells compatible senders to always use properly authenticated TLS when talking to your server, offering a simple-to-deploy way to protect your server against MitM attacks on port 25.

Basically, you to create a file with following contents and make it available at https://mta-sts.example.org/.well-known/mta-sts.txt:

mode: enforce
max_age: 604800
mx: example.org

Note: example.org in the file is your MX hostname, example.org in URL is the domain you are receiving messages for. In simple configurations, they are going to be the same, but this is not the case for more complex setups. If you have multiple MX servers - add them all once per line, like that:

mx: mx1.example.org
mx: mx2.example.org

postmaster and other user accounts

A mail server is useless without mailboxes, right? Unlike software like postfix and dovecot, maddy uses "virtual users" by default, meaning it does not care or know about system users.

Here is the command to create virtual 'postmaster' account, it will prompt you for a password:

$ maddyctl users create postmaster@example.org

Note that account names include the domain. When authenticating in the mail client, full address should be specified as a username as well.

Btw, it is a good idea to learn what else maddyctl can do. Given the non-standard structure of messages storage, maddyctl is the only way to comfortably inspect it.

Optional: Install and use fail2ban

The email world is full of annoying bots just like Web (these annoying scanners looking for PhpMyAdmin on your blog). fail2ban can help you get rid of them by temporary blocking offending IPs.

1. Install the fail2ban package using your distribution package manager For Debian-based distributions:

apt-get install fail2ban

2. build.sh already installed necessary jail configuration files, but you have to enable them. Open /etc/fail2ban/jail.d/common.local (create one if needed) and add the following lines:

[maddy-auth]
enabled = true

[maddy-dictonary-attack]
enabled = true

Now start or restart the fail2ban daemon:

systemctl restart fail2ban

Keep in mind that the maddy jail configuration uses a different much longer bantime value. This means users will get IP-banned for quite a long time (4 days) after 5 failed login attempts. You might want to change that to a smaller period by editing /etc/fail2ban/jail.d/common.local:

[maddy-auth]
bantime = 1h