title: Set up a Mail server with Postfix, Dovecot, SpamAssassin and OpenDKIM author: David Luévano lang: en summary: How to set up a Mail server using Postfix, Dovecot, SpamAssassin and OpenDKIM, on Arch. This is a follow up on post about creating a website with Nginx and Certbot. tags: server tools code tutorial english The entry is going to be long because it's a *tedious* process. This is also based on [Luke Smith's script](https://github.com/LukeSmithxyz/emailwiz), but adapted to Arch Linux (his script works on debian-based distributions). This entry is mostly so I can record all the notes required while I'm in the process of installing/configuring the mail server on a new VPS of mine; ~~also I'm going to be writing a script that does everything in one go (for Arch Linux), that will be hosted [here](https://git.luevano.xyz/server_scripts.git).~~ ^^I haven't had time to do the script so nevermind this, if I ever do it I'll make a new entry regarding it.^^ This configuration works for local users (users that appear in `/etc/passwd`), and does not use any type of SQL database. And note that most if not all commands executed here are run with root privileges, unless stated otherwise. # Table of contents [TOC] # Prerequisites Basically the same as with the [website with Nginx and Certbot](https://blog.luevano.xyz/a/website_with_nginx.html), with the extras: - You will need a **CNAME** for "mail" and (optionally) "www.mail", or whatever you want to call the sub-domains (although the [RFC 2181](https://tools.ietf.org/html/rfc2181#section-10.3) states that it NEEDS to be an **A** record, fuck the police). - An SSL certificate. You can use the SSL certificate obtained following my last post using `certbot` (just create a `mail.conf` and run `certbot --nginx` again). - Ports `25`, `587` (SMTP), `465` (SMTPS), `143` (IMAP) and `993` (IMAPS) open on the firewall (I use `ufw`). # Postfix [Postfix](https://wiki.archlinux.org/title/postfix) is a "mail transfer agent" which is the component of the mail server that receives and sends emails via SMTP. Install the `postfix` package: ```sh pacman -S postfix ``` We have two main files to configure (inside `/etc/postfix`): `master.cf` ([master(5)](https://man.archlinux.org/man/master.5)) and `main.cf` ([postconf(5)](https://man.archlinux.org/man/postconf.5)). We're going to edit `main.cf` first either by using the command `postconf -e 'setting'` or by editing the file itself (I prefer to edit the file). Note that the default file itself has a lot of comments with description on what each thing does (or you can look up the manual, linked above), I used what Luke's script did plus some other settings that worked for me. Now, first locate where your website cert is, mine is at the default location `/etc/letsencrypt/live/`, so my `certdir` is `/etc/letsencrypt/live/luevano.xyz`. Given this information, change `{yourcertdir}` on the corresponding lines. The configuration described below has to be appended in the `main.cf` configuration file. Certificates and ciphers to use for authentication and security: ```apache smtpd_tls_key_file = {yourcertdir}/privkey.pem smtpd_tls_cert_file = {yourcertdir}/fullchain.pem smtpd_use_tls = yes smtpd_tls_auth_only = yes smtp_tls_security_level = may smtp_tls_loglevel = 1 smtp_tls_CAfile = {yourcertdir}/cert.pem smtpd_tls_mandatory_protocols = !SSLv2, !SSLv3, !TLSv1, !TLSv1.1 smtp_tls_mandatory_protocols = !SSLv2, !SSLv3, !TLSv1, !TLSv1.1 smtpd_tls_protocols = !SSLv2, !SSLv3, !TLSv1, !TLSv1.1 smtp_tls_protocols = !SSLv2, !SSLv3, !TLSv1, !TLSv1.1 tls_preempt_cipherlist = yes smtpd_tls_exclude_ciphers = aNULL, LOW, EXP, MEDIUM, ADH, AECDH, MD5, DSS, ECDSA, CAMELLIA128, 3DES, CAMELLIA256, RSA+AES, eNULL smtp_tls_CApath = /etc/ssl/certs smtpd_tls_CApath = /etc/ssl/certs smtpd_relay_restrictions = permit_sasl_authenticated, permit_mynetworks, defer_unauth_destination ``` Also, for the *connection* with `dovecot`, append the next few lines (telling postfix that `dovecot` will use user/password for authentication): ```apache smtpd_sasl_auth_enable = yes smtpd_sasl_type = dovecot smtpd_sasl_path = private/auth smtpd_sasl_security_options = noanonymous, noplaintext smtpd_sasl_tls_security_options = noanonymous ``` Specify the mailbox home, this is going to be a directory inside your user's home containing the actual mail files, for example it will end up being`/home/david/Mail/Inbox`: ```apache home_mailbox = Mail/Inbox/ ``` Pre-configuration to work seamlessly with `dovecot` and `opendkim`: ```apache myhostname = {yourdomainname} mydomain = localdomain mydestination = $myhostname, localhost.$mydomain, localhost milter_default_action = accept milter_protocol = 6 smtpd_milters = inet:127.0.0.1:8891 non_smtpd_milters = inet:127.0.0.1:8891 mailbox_command = /usr/lib/dovecot/deliver ``` Where `{yourdomainname}` is `luevano.xyz` in my case. Lastly, if you don't want the sender's IP and user agent (application used to send the mail), add the following line: ```apache smtp_header_checks = regexp:/etc/postfix/smtp_header_checks ``` And create the `/etc/postfix/smtp_header_checks` file with the following content: ```coffee /^Received: .*/ IGNORE /^User-Agent: .*/ IGNORE ``` That's it for `main.cf`, now we have to configure `master.cf`. This one is a bit more tricky. First look up lines (they're uncommented) `smtp inet n - n - - smtpd`, `smtp unix - - n - - smtp` and `-o syslog_name=postfix/$service_name` and either delete or uncomment them... or just run `sed -i "/^\s*-o/d;/^\s*submission/d;/\s*smtp/d" /etc/postfix/master.cf` as stated in Luke's script. Lastly, append the following lines to complete postfix setup and pre-configure for `spamassassin`. ```txt smtp unix - - n - - smtp smtp inet n - y - - smtpd -o content_filter=spamassassin submission inet n - y - - smtpd -o syslog_name=postfix/submission -o smtpd_tls_security_level=encrypt -o smtpd_sasl_auth_enable=yes -o smtpd_tls_auth_only=yes smtps inet n - y - - smtpd -o syslog_name=postfix/smtps -o smtpd_tls_wrappermode=yes -o smtpd_sasl_auth_enable=yes spamassassin unix - n n - - pipe user=spamd argv=/usr/bin/vendor_perl/spamc -f -e /usr/sbin/sendmail -oi -f \${sender} \${recipient} ``` Now, I ran into some problems with postfix, one being [smtps: Servname not supported for ai_socktype](https://www.faqforge.com/linux/fix-for-opensuse-error-postfixmaster-fatal-0-0-0-0smtps-servname-not-supported-for-ai_socktype/), to fix it, as *Till* posted in that site, edit `/etc/services` and add: ```apache smtps 465/tcp smtps 465/udp ``` Before starting the `postfix` service, you need to run `newaliases` first, but you can do a bit of configuration beforehand editing the file `/etc/postfix/aliases`. I only change the `root: you` line (where `you` is the account that will be receiving "root" mail). After you're done, run: ```sh postalias /etc/postfix/aliases newaliases ``` At this point you're done configuring `postfix` and you can already start/enable the `postfix` service: ```sh systemctl start postfix.service systemctl enable postfix.service ``` # Dovecot [Dovecot](https://wiki.archlinux.org/title/Dovecot) is an IMAP and POP3 server, which is what lets an email application retrieve the mail. Install the `dovecot` and `pigeonhole` (sieve for `dovecot`) packages: ```sh pacman -S dovecot pigeonhole ``` On arch, by default, there is no `/etc/dovecot` directory with default configurations set in place, but the package does provide the example configuration files. Create the `dovecot` directory under `/etc` and, optionally, copy the `dovecot.conf` file and `conf.d` directory under the just created `dovecot` directory: ```sh mkdir /etc/dovecot cp /usr/share/doc/dovecot/example-config/dovecot.conf /etc/dovecot/dovecot.conf cp -r /usr/share/doc/dovecot/example-config/conf.d /etc/dovecot ``` As Luke stated, `dovecot` comes with a lot of "modules" (under `/etc/dovecot/conf.d/` if you copied that folder) for all sorts of configurations that you can include, but I do as he does and just edit/create the whole `dovecot.conf` file; although, I would like to check each of the separate configuration files `dovecot` provides I think the options Luke provides are more than good enough. I'm working with an empty `dovecot.conf` file. Add the following lines for SSL and login configuration (also replace `{yourcertdir}` with the same certificate directory described in the Postfix section above, note that the `<` is required): ```apache ssl = required ssl_cert = <{yourcertdir}/fullchain.pem ssl_key = <{yourcertdir}/privkey.pem ssl_min_protocol = TLSv1.2 ssl_cipher_list = ALL:!RSA:!CAMELLIA:!aNULL:!eNULL:!LOW:!3DES:!MD5:!EXP:!PSK:!SRP:!DSS:!RC4:!SHA1:!SHA256:!SHA384:!LOW@STRENGTH ssl_prefer_server_ciphers = yes ssl_dh =