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# Start here

Good to have you here. This is the 12th edition of the ISPmail guide. A free guide to setting up a mail server for friends and family using open-source software. Email on the internet nowadays is in the hands of few huge companies. Take back control and host your own mail server. Get a cheap virtual server and read along. This guide is comprehensive and will walk you through everything you need to know. I am publishing this guide without any commercial motives. All you need to invest is your time. And thanks to Debian you will get automatic security updates and do not have to worry about anything until the next stable release comes out in 2-3 years. And perhaps you come back then to upgrade your server.

## What your mail server will do

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- Receive emails on (multiple) domains.
- Filter out spam.
- Send emails out to the internet. Connections will be encrypted when possible.
- Store as many emails for as many email addresses as you have disk space. Set limits (“quotas”) per user. The only limit is the size of your disk.
- Have a webmail interface so users can access their emails securely from any location using a web browser.
- Let your users fetch email using IMAP and send email through your servers using SMTP.
- Add automatic cryptographic signatures using DKIM to outgoing emails to prove that you are the owner of your domain.
- Allow users to manage server-based filter rules. Distribute incoming emails to different folders. Forward copies. Or send out-of-office notifications.
- Mitigate brute force attacks.

## What you will need

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- Linux experience. Preferably a Debian-derivative. No godlike skills required. But know your basics: navigating the file system, editing files, watching log files. Have some basic understanding of DNS. Bonus points if you have played with an SQL database and know about SELECT, INSERT, rows, columns.
- Time. 2 hours to get the basic service running. Maybe a day if you are not an everyday Debian user.
- A server that runs Debian Trixie. 1 GB of RAM and a 20 GB disk/SSD is fine for your friends and family. Just rent a cheap virtual server. Other distributions than Debian come with other versions of the software and have different configurations and paths on disk. It will work but you will need to deviate from this guide and do some research. So for the smoothest ride go with Debian.
- The hosting provider you chose to run your server on needs to allow SMTP send and receive. These providers are known to be troublesome:
  - Hetzner (DE, FI, US): Will allow SMTP after a month of paying for their service and per a request issued at https://console.hetzner.cloud/limits
  - DigitalOcean (US): Blocks SMTP and tells you that running your own mail server is a bad idea. Avoid.
- Your server needs to have a public IP address that does not belong to a range of typical ISP customers. You usually can’t operate the mail server from a residential IP address at home because those IP ranges are blacklisted by most other mail servers. Make sure that your IP address is not blacklisted before you start. If you rent a virtual server from your favorite hosting company you probably won’t have any problems. But if you want to run the service from your home, this is something you need to check.
- An internet domain (or several) to receive emails for. You need to be able to set A, MX and TXT records for that domain. You should also be able to set PTR records for your IP address because some mail servers on the internet require you to have matching forward and reverse DNS records.
- Patience. We will proceed slowly and after every step ensure that you are still on track. Don’t hurry and skip parts even if they appear confusing at first. If you get lost just submit your question at the bottom of any page throughout this guide and help is on the way. Or join the chat channel.

## What this is not about

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If you just want to have a working mail server and do not care how it works then this guide may not be for you. There is an automated installation script that does all the steps of this guide automatically for you. But that is no replacement for reading this guide and understanding how the server works. It is merely meant to help you save time if you want to set up multiple servers.

Be aware that running a mail server requires some technical understanding. And that’s what the ISPmail guide is for. Experience from giving support to other sysadmins shows that most problems appear because some detail in a complex setup goes wrong and they have no idea how to fix it. Email has evolved a lot over the past 40 years. Go with ready solutions if you like. But I have a feeling that we meet again. And you will probably not save time either taking the supposedly easy route.

There are also other projects that give you a ready solution like mailinabox, iRedMail or Mailcow.

## What’s new

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The last updates to this guide – up to Debian Bookworm – were mainly minor changes. However this time I have spent many weeks to improve the guide. Most sections are completely rewritten. Explanations about SMTP versus submission were added. I dived deep into RFCs and reference documentation. I have used more features of the Astro/Starlight framework (the software that is used to render this guide) to add visual guides like task lists or image galleries or foldout sections to help you understand what’s going on on a mail server without getting lost. And I have replaced all my configuration examples with blocks that you can copy/paste into your shell. So this guide is supposed to be shorter and faster to follow while at the same time trying to be more comprehensive. Please leave your feedback in the comment sections whether this approach appeals to you.

## Ready?

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The entire tutorial is split into several pages. You can find the different chapters on the left. The navigation within a chapter can be found on the right. Let’s go.