Set up Postfix for incoming email

本文将带你通过s的步骤etting up a basic Postfix mail server with IMAP authentication on Ubuntu, to be used withincoming email.

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

Configure your server firewall

Open up port 25 on your server so that people can send email into the server over SMTP.
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

Install thepostfixpackage if it is not installed already:
```
sudoapt-getinstallpostfix
```
When asked about the environment, select 'Internet Site'. When asked to confirm the hostname, make sure it matchesgitlab.example.com.
Install themailutilspackage.
```
sudoapt-getinstallmailutils
```

Create user

Create a user for incoming email.
```
sudouseradd-m-s/bin/bash incoming
```
Set a password for this user.
```
sudopasswd incoming
```
Be sure not to forget this, you'll need it later.

Test the out-of-the-box setup

Connect to the local SMTP server:

telnet localhost 25

You should see a prompt like this:

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

If you get aConnection refusederror instead, verify thatpostfixis running:

sudopostfix status

If it is not, start it:

sudopostfix start

Send the newincominguser a dummy email to test SMTP, by entering the following into the SMTP prompt:
```
ehlo localhostmail from: root@localhostrcpt to: incoming@localhostdataSubject: Re: Some issueSounds good!.quit
```
Note:The.is a literal period on its own line.
Note:If you receive an error after enteringrcpt to: incoming@localhostthen your Postfixmy_network配置是不正确的。The error will say 'Temporary lookup failure'. SeeConfigure Postfix to receive email from the Internet.

Check if theincominguser received the email:

su - incomingmail

You should see output like this:

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

Quit the mail app:

Log out of theincomingaccount and go back to beingroot:
```
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.

Configure Postfix to use Maildir-style mailboxes:
```
sudopostconf-e"home_mailbox = Maildir/"
```
Restart Postfix:
```
sudo/etc/init.d/postfix restart
```
Test the new setup:
1. Follow steps 1 and 2 ofTest the out-of-the-box setup.
2. Check if theincominguser received the email:
```
su - incomingMAIL=/home/incoming/Maildirmail
```
  You should see output like this:
```
"/home/incoming/Maildir": 1 message 1 unread>U 1 root@localhost 59/2842 Re: Some issue
```
  Quit the mail app:
```
q
```
Note:Ifmailreturns an errorMaildir: Is a directorythen your version ofmaildoesn't support Maildir style mailboxes. Installheirloom-mailxby runningsudo apt-get install heirloom-mailx. Then, try the above steps again, substitutingheirloom-mailxfor themailcommand.
Log out of theincomingaccount and go back to beingroot:
```
logout
```

Install the Courier IMAP server

Install thecourier-imappackage:
```
sudoapt-getinstallcourier-imap
```
And startimapd:
```
imapd start
```
The courier-authdaemon isn't started after installation. Without it, imap authentication will fail:
```
sudoservice courier-authdaemon start
```
You can also configure courier-authdaemon to start on boot:
```
sudosystemctlenablecourier-authdaemon
```

Configure Postfix to receive email from the internet

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

sudopostconf-e"mydestination = gitlab.example.com, localhost.localdomain, localhost"

Let Postfix know about the IPs that it should consider part of the LAN:
We'll assume192.168.1.0/24is your local LAN. You can safely skip this step if you don't have other machines in the same local network.
```
sudopostconf-e"mynetworks = 127.0.0.0/8, 192.168.1.0/24"
```
Configure Postfix to receive mail on all interfaces, which includes the internet:
```
sudopostconf-e"inet_interfaces = all"
```
Configure Postfix to use the+delimiter for sub-addressing:
```
sudopostconf-e"recipient_delimiter = +"
```
Restart Postfix:
```
sudoservice postfix restart
```

测试最终的设置

Test SMTP under the new setup:
1. Connect to the SMTP server:
```
telnet gitlab.example.com 25
```
  You should see a prompt like this:
```
Trying 123.123.123.123...Connected to gitlab.example.com.Escape character is'^]'.220 gitlab.example.com ESMTP Postfix(Ubuntu)
```
  If you get aConnection refusederror instead, make sure your firewall is setup to allow inbound traffic on port 25.
2. Send theincominguser a dummy email to test SMTP, by entering the following into the SMTP prompt:
```
ehlo gitlab.example.commail from: root@gitlab.example.comrcpt to: incoming@gitlab.example.comdataSubject: Re: Some issueSounds good!.quit
```
  (Note: The.is a literal period on its own line)
3. Check if theincominguser received the email:
```
su - incomingMAIL=/home/incoming/Maildirmail
```
  You should see output like this:
```
"/home/incoming/Maildir": 1 message 1 unread>U 1 root@gitlab.example.com 59/2842 Re: Some issue
```
  Quit the mail app:
```
q
```
4. Log out of theincomingaccount and go back to beingroot:
```
logout
```

Test IMAP under the new setup:

Connect to the IMAP server:

telnet gitlab.example.com 143

You should see a prompt like this:

Trying 123.123.123.123...Connected to mail.example.gitlab.com.Escape character is'^]'.- OK[CAPABILITY IMAP4rev1 UIDPLUS CHILDREN NAMESPACETHREAD=ORDEREDSUBJECTTHREAD=REFERENCES SORT QUOTA IDLE ACLACL2=UNION] Courier-IMAP ready. Copyright 1998-2011 Double Precision, Inc. See COPYINGfordistribution information.

Sign in as theincominguser to test IMAP, by entering the following into the IMAP prompt:
```
a login incoming PASSWORD
```
Replace PASSWORD with the password you set on theincominguser earlier.
You should see output like this:
```
a OK LOGIN Ok.
```
Disconnect from the IMAP server:
```
alogout
```

Done!

If all the tests were successful, Postfix is all set up and ready to receive email! Continue with theincoming emailguide to configure GitLab.

This document was adapted fromhttps://help.ubuntu.com/community/PostfixBasicSetupHowto, by contributors to the Ubuntu documentation wiki.