Raspberry Pi Email Server

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The RasPi’s small size and low power consumption make it an ideal choice for use as a home email server. After trying a couple of different pieces of software, I finally found an excellent combination: Postfix with Dovecot and Squirrelmail, plus Spamasssassin and Sieve for spam filtering.

There are many, many tutorials out there for the first trilogy of programs, but since the configuration is slightly different for each distribution I kept coming unstuck when setting mine up on the Pi. Having finally got mine configured properly, I’ve put together a set of 5 tutorials, which will take you from a vanilla Raspbian image to a fully functioning email server in no time.

When writing the tutorial I made an effort to explain what each setting does instead of just dumping commands. With a bit of luck at the end of the process you’ll not only have a working server, you’ll understand how it works… without having to wade through reams of documentation like I did!

If you follow the tutorials from start to finish, here’s what you’ll end up with:

  1. An email server that you can run 24/7/365 for under £5 of electricity per year
  2. Personalised email address like you@yourdomain.com (requires you to have registered a domain name with a registrar like namecheap.com - see my DNS basics tutorial)
  3. The ability to connect from anywhere, and read & send email, using a secure IMAP connection on your phone, tablet or computer
  4. Log in to webmail using any web browser on a secure HTTPS connection, read & send email
  5. Complete control over your personal communication. Your emails are stored on YOUR server, and nobody is scanning them to sell you adverts.
  6. Smart spam filtering with Spamassassin
  7. Customisable mail sorting with Sieve rules

Postfix, the Mail Transfer Agent

Postfix Logo
Postfix is the program that lets you send and receive email using Simple Mail Transfer Protocol (SMTP). Whilst you, the user, may connect to your email server using IMAP (on port 143 or 993), or POP (on port 110 or 995), email servers talk to each other using SMTP on port 25.

So, this is the basic core of the server. Without it, you wouldn’t be able to send or receive any emails!

I’ve covered the setup here:
Raspberry Pi Email Server Part 1: Postfix

Dovecot, the POP/IMAP Server

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Dovecot is used for two things:

  1. It provides you with IMAP functionality
  2. It checks that you are who you say you are using Simple Authentication and Security Layer (SASL) before you send or fetch mail

If you’re not interested in connecting with IMAP on your devices, you still need Dovecot. Not only is it doing SASL for you, but Squirrelmail connects using IMAP in order to provide you with webmail.

I’ve covered Dovecot installation and configuration here:
Raspberry Pi Email Server Part 2: Dovecot

Squirrelmail, for Webmail

Squirrelmail Logo
Squirrelmail is handy because it allows you to check your email in any browser, from anywhere.

Of the first three, it’s probably the easiest to configure. I’ve covered it here:
Raspberry Pi Email Server Part 3: Squirrelmail

Spamassassin, for Marking Spam

Spamassassin Logo
Spamassassin is the program that we will use to audit incoming mail and decide whether or not it’s spam. Spamassassin doesn’t actually sort the mail into the spam folder, it only changes information in the headers based on the results of the scan. I’ve covered it here: Raspberry Pi Email Server Part 4: Spam Detection with Spamassassin.

LMTP & Sieve for Spam Sorting & Mailbox Organisation

After Spamassassin has checked incoming mail to see if it’s spam or not, we need another program to sort it into the right mail folder. This final step will be done with Dovecot’s Local Mail Transfer Protocol (LMTP) daemon and a Sieve plugin.

Sieve is a simple programming language that allows users to define what to do with incoming email based on a predefined set of rules – think “if the header contains this flag, put it in the spam folder” kind of thing and you’ll get the gist. Aside from spam filtering, Sieve can be used to automatically sort & de-clutter your inbox. These steps are covered in the final tutorial: Raspberry Pi Email Server Part 5: Spam Sorting with LMTP & Sieve

Enjoy! I’d love to hear how you get on, so leave a comment below :)

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Comments

Hi,

It probably could handle the load, but the hardware is not something I would want to rely on for a business, it's quite easy to get SD card corruption etc. and lose everything.

You should be able to use this guide on any debian derivative (debian, raspbian, ubuntu) on any hardware though.

Sam

Hello,

I was thinking of setting up this emails server on my raspberry pi.. I have one question.

Is there a way to have the messages and attachments saved to an external drive ?? I have a 32G card on my pi now but it could fill up fast with a lot of emails and attachments. is there a way if I attach an external USB hard drive to the pi to have the messages and attachments saved in a folder on the external drive so I can have more storage ?

thanks for any help.

Hey Sam, Really good tutorial.
However when I send emails to my old gmail account, it says it wasn't encrypted.
I'm sending through port 587, and I have a letsencrypt certificate properly installed.
The logs don't show any errors.

Ben,

Well spotted, I've been meaning to add that to the tutorial (for years, actually!).

Set smtp_tls_security_level = may in /etc/postfix/main.cf.

A value of may means your server will use TLS if it is supported by the other server, encrypt means TLS is required and no email will be sent without TLS (which might mean you can't send email to some people).

The corresponding setting for incoming email is smtpd_tls_security_level.

Sam

Brilliant, thanks for that!

Of note, I noticed it said the smtpd_tls_security_level setting overrides the smtpd_use_tls setting set by the tutorial, so I removed that. it works great both ways.

That's weird. Are you logged in locally using a screen or via SSH?

You can try again with sudo dpkg-reconfigure postfix

Sam

i wish i would of done some of these tutorials a decade ago, but is not late.

Great job i hope a younger generation start adopting these tips ASAP

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