# Set up Postfix for incoming email

This document will take you through the steps of setting up a basic Postfix mail
server with IMAP authentication on Ubuntu, to be used with [incoming email](incoming_email.md).

The instructions make the assumption that you will be using the email address `incoming@gitlab.example.com`, that is, username `incoming` on host `gitlab.example.com`. Don't forget to change it to your actual host when executing the example code snippets.

## Configure your server firewall

1. Open up port 25 on your server so that people can send email into the server over SMTP.
1. If the mail server is different from the server running GitLab, open up port 143 on your server so that GitLab can read email from the server over IMAP.

## Install packages

1. Install the `postfix` package if it is not installed already:

   ```shell
   sudo apt-get install postfix
   ```

   When asked about the environment, select 'Internet Site'. When asked to confirm the hostname, make sure it matches `gitlab.example.com`.

1. Install the `mailutils` package.

   ```shell
   sudo apt-get install mailutils
   ```

## Create user

1. Create a user for incoming email.

   ```shell
   sudo useradd -m -s /bin/bash incoming
   ```

1. Set a password for this user.

   ```shell
   sudo passwd incoming
   ```

   Be sure not to forget this, you'll need it later.

## Test the out-of-the-box setup

1. Connect to the local SMTP server:

   ```shell
   telnet localhost 25
   ```

   You should see a prompt like this:

   ```shell
   Trying 127.0.0.1...
   Connected to localhost.
   Escape character is '^]'.
   220 gitlab.example.com ESMTP Postfix (Ubuntu)
   ```

   If you get a `Connection refused` error instead, verify that `postfix` is running:

   ```shell
   sudo postfix status
   ```

   If it is not, start it:

   ```shell
   sudo postfix start
   ```

1. Send the new `incoming` user an email to test SMTP, by entering the following into the SMTP prompt:

   ```plaintext
   ehlo localhost
   mail from: root@localhost
   rcpt to: incoming@localhost
   data
   Subject: Re: Some issue

   Sounds good!
   .
   quit
   ```

   _**Note:** The `.` is a literal period on its own line._

   _**Note:** If you receive an error after entering `rcpt to: incoming@localhost`
   then your Postfix `my_network` configuration is not correct. The error will
   say 'Temporary lookup failure'. See
   [Configure Postfix to receive email from the Internet](#configure-postfix-to-receive-email-from-the-internet)._

1. Check if the `incoming` user received the email:

   ```shell
   su - incoming
   mail
   ```

   You should see output like this:

   ```plaintext
   "/var/mail/incoming": 1 message 1 unread
   >U   1 root@localhost                           59/2842  Re: Some issue
   ```

   Quit the mail app:

   ```shell
   q
   ```

1. Sign out of the `incoming` account, and go back to being `root`:

   ```shell
   logout
   ```

## Configure Postfix to use Maildir-style mailboxes

Courier, which we will install later to add IMAP authentication, requires mailboxes to have the Maildir format, rather than mbox.

1. Configure Postfix to use Maildir-style mailboxes:

   ```shell
   sudo postconf -e "home_mailbox = Maildir/"
   ```

1. Restart Postfix:

   ```shell
   sudo /etc/init.d/postfix restart
   ```

1. Test the new setup:

   1. Follow steps 1 and 2 of _[Test the out-of-the-box setup](#test-the-out-of-the-box-setup)_.
   1. Check if the `incoming` user received the email:

      ```shell
      su - incoming
      MAIL=/home/incoming/Maildir
      mail
      ```

      You should see output like this:

      ```plaintext
      "/home/incoming/Maildir": 1 message 1 unread
      >U   1 root@localhost                           59/2842  Re: Some issue
      ```

      Quit the mail app:

      ```shell
      q
      ```

   _**Note:** If `mail` returns an error `Maildir: Is a directory` then your
   version of `mail` doesn't support Maildir style mailboxes. Install
   `heirloom-mailx` by running `sudo apt-get install heirloom-mailx`. Then,
   try the above steps again, substituting `heirloom-mailx` for the `mail`
   command._

1. Sign out of the `incoming` account, and go back to being `root`:

   ```shell
   logout
   ```

## Install the Courier IMAP server

1. Install the `courier-imap` package:

   ```shell
   sudo apt-get install courier-imap
   ```

   And start `imapd`:

   ```shell
   imapd start
   ```

1. The `courier-authdaemon` isn't started after installation. Without it, IMAP authentication will fail:

   ```shell
   sudo service courier-authdaemon start
   ```

   You can also configure `courier-authdaemon` to start on boot:

   ```shell
   sudo systemctl enable courier-authdaemon
   ```

## Configure Postfix to receive email from the internet

1. Let Postfix know about the domains that it should consider local:

   ```shell
   sudo postconf -e "mydestination = gitlab.example.com, localhost.localdomain, localhost"
   ```

1. Let Postfix know about the IPs that it should consider part of the LAN:

   We'll assume `192.168.1.0/24` is your local LAN. You can safely skip this step if you don't have other machines in the same local network.

   ```shell
   sudo postconf -e "mynetworks = 127.0.0.0/8, 192.168.1.0/24"
   ```

1. Configure Postfix to receive mail on all interfaces, which includes the internet:

   ```shell
   sudo postconf -e "inet_interfaces = all"
   ```

1. Configure Postfix to use the `+` delimiter for sub-addressing:

   ```shell
   sudo postconf -e "recipient_delimiter = +"
   ```

1. Restart Postfix:

   ```shell
   sudo service postfix restart
   ```

## Test the final setup

1. Test SMTP under the new setup:

   1. Connect to the SMTP server:

      ```shell
      telnet gitlab.example.com 25
      ```

      You should see a prompt like this:

      ```shell
      Trying 123.123.123.123...
      Connected to gitlab.example.com.
      Escape character is '^]'.
      220 gitlab.example.com ESMTP Postfix (Ubuntu)
      ```

      If you get a `Connection refused` error instead, make sure your firewall is set up to allow inbound traffic on port 25.

   1. Send the `incoming` user an email to test SMTP, by entering the following into the SMTP prompt:

      ```plaintext
      ehlo gitlab.example.com
      mail from: root@gitlab.example.com
      rcpt to: incoming@gitlab.example.com
      data
      Subject: Re: Some issue

      Sounds good!
      .
      quit
      ```

      (Note: The `.` is a literal period on its own line)

   1. Check if the `incoming` user received the email:

      ```shell
      su - incoming
      MAIL=/home/incoming/Maildir
      mail
      ```

      You should see output like this:

      ```plaintext
      "/home/incoming/Maildir": 1 message 1 unread
      >U   1 root@gitlab.example.com                           59/2842  Re: Some issue
      ```

      Quit the mail app:

      ```shell
      q
      ```

   1. Sign out of the `incoming` account, and go back to being `root`:

      ```shell
      logout
      ```

1. Test IMAP under the new setup:

   1. Connect to the IMAP server:

      ```shell
      telnet gitlab.example.com 143
      ```

      You should see a prompt like this:

      ```shell
      Trying 123.123.123.123...
      Connected to mail.gitlab.example.com.
      Escape character is '^]'.
      - OK [CAPABILITY IMAP4rev1 UIDPLUS CHILDREN NAMESPACE THREAD=ORDEREDSUBJECT THREAD=REFERENCES SORT QUOTA IDLE ACL ACL2=UNION] Courier-IMAP ready. Copyright 1998-2011 Double Precision, Inc.  See COPYING for distribution information.
      ```

   1. Sign in as the `incoming` user to test IMAP, by entering the following into the IMAP prompt:

      ```plaintext
      a login incoming PASSWORD
      ```

      Replace PASSWORD with the password you set on the `incoming` user earlier.

      You should see output like this:

      ```plaintext
      a OK LOGIN Ok.
      ```

   1. Disconnect from the IMAP server:

      ```shell
      a logout
      ```

## Done

If all the tests were successful, Postfix is all set up and ready to receive email! Continue with the [incoming email](incoming_email.md) guide to configure GitLab.

---

_This document was adapted from <https://help.ubuntu.com/community/PostfixBasicSetupHowto>, by contributors to the Ubuntu documentation wiki._
