Mail
Now that we have our basic mail infrastructure working, we will add support for rspamd and enable DKIM signing of our messages.
In this series we will set up a fully-featured mail server in a FreeBSD jail using OpenSMTPd, Dovecot and rspamd. In contrast to many other guides, this one is split into multiple posts that can either be read and followed individually, or as a whole. After each post, you end up with a fully working system (that might lack some features ;)).
In this part of the FreeBSD mail server, we build on the recent two posts where we set up the IMAP and SMTP and extend our configuration to support virtual users, which means that we don’t autenticate with system users anymore and, alongside, hand over the incoming email management to Dovecot by providing email from OpenSMTPd to Dovecot using LMTP. Since both daemons will not work together more closely, we will also unify the login credentials in a single passwd-style file that can be read from both OpenSMTPd and Dovecot.
This is a follow-up post to the initial FreeBSD mail server article that I posted a few weeks ago. In this step, we will build upon what we set up in the first part and add the possibility to fetch email from a mail client using IMAP. We will still use system users for authentication, before we switch to virtual users in the next step.
In this series we will set up a fully-featured mail server in a FreeBSD jail using OpenSMTPd, Dovecot and rspamd. In contrast to many other guides, this one is split into multiple posts that can either be read and followed individually, or as a whole. After each post, you end up with a fully working system (that might lack some features ;)).
I run mail servers for many years now, but I was never brave enough to set up one from scratch for my daily mail. So I always fell back to pre-configured solutions like docker-mailserver, Mailcow, or in case of FreeBSD to iRedMail. My biggest pain point was the secure configuration of Postfix. When I discovered OpenSMTPd, I decided that it’s the right time now to finally build a fully-featured mail server setup from scratch including virtual users, spam filter etc.
I have so many accounts for various web-based solutions, I barely can remember a few. And they send emails. So many that it’s sometimes hard to not loose the overview in my mailbox.
When you run your own mail server, it’s easy to set up a dynamic aliases for your mailserver based on a regular expression pattern that allows to e.g. have a own email address for each service you register. The emails sent to that alias go into special mailboxes instead of your default INBOX folder. This is called “subaddressing”, sometimes also referred to as “plus addressing” or “tagged addressing”.
FreeBSD is shipped with sendmail as the default MTA, which is configured to local delivery on a vanilla installation.
Therefore many people don’t even recognize one of FreeBSDs great features for system administrators: FreeBSD sends
system status emails through periodic(8)…
It’s more than likely that your email provider of choice, especially the ones
that offer mail services free of charge, will not support receiving email to
custom domain names like, in my case, davd.net. Running your own mail server would
solve this problem but running a fully featured mail stack including POP, IMAP,
Sieve filters et cetera requires a fairly powerful machine.
Additionally, if not configured properly, there’s big potential for abuse,
e.g. spam.
As an alternative, it’s possible to just run a MTA which redirects all incoming email
to an external mail server.
This can be ran on almost any machine, even on a low-budget computer like the
Raspberry Pi or a cheap virtual server.
