如何在 CentOS 8 上安装和配置 Postfix 邮件服务器
Postfix 邮件
Postfix 是一个自由开源的 MTA（邮件传输代理），用于在 Linux 系统上路由或传递电子邮件。在本指南中，你将学习如何在 CentOS 8 上安装和配置 Postfix。


![Install-configure-Postfx-Server-CentOS8](/data/attachment/album/201911/21/072857e9bvnzrbqayraxva.jpg)


实验室设置：


* 系统：CentOS 8 服务器
* IP 地址：192.168.1.13
* 主机名：server1.crazytechgeek.info（确保域名指向服务器的 IP）


### 步骤 1）更新系统


第一步是确保系统软件包是最新的。为此，请按如下所示更新系统：



```
# dnf update
```

继续之前，还请确保不存在其他 MTA（如 Sendmail），因为这将导致与 Postfix 配置冲突。例如，要删除 Sendmail，请运行以下命令：



```
# dnf remove sendmail
```

### 步骤 2）设置主机名并更新 /etc/hosts


使用下面的 `hostnamectl` 命令在系统上设置主机名：



```
# hostnamectl set-hostname server1.crazytechgeek.info
# exec bash
```

此外，你需要在 `/etc/hosts` 中添加系统的主机名和 IP：



```
# vim /etc/hosts
192.168.1.13   server1.crazytechgeek.info
```

保存并退出文件。


### 步骤 3）安装 Postfix 邮件服务器


验证系统上没有其他 MTA 在运行后，运行以下命令安装 Postfix：



```
# dnf install postfix
```

![Install-Postfix-Centos8](/data/attachment/album/201911/21/072858z06i6mz66qil576w.png)


### 步骤 4）启动并启用 Postfix 服务


成功安装 Postfix 后，运行以下命令启动并启用 Postfix 服务：



```
# systemctl start postfix
# systemctl enable postfix
```

要检查 Postfix 状态，请运行以下 `systemctl` 命令：



```
# systemctl status postfix
```

![Start-Postfix-check-status-centos8](/data/attachment/album/201911/21/072900e6thztbhncn6ulk5.png)


太好了，我们已经验证了 Postfix 已启动并正在运行。接下来，我们将配置 Postfix 从本地发送邮件到我们的服务器。


### 步骤 5）安装 mailx 邮件客户端


在配置 Postfix 服务器之前，我们需要安装 `mailx`，要安装它，请运行以下命令：



```
# dnf install mailx
```

![Install-Mailx-CentOS8](/data/attachment/album/201911/21/072901e9vhlvwiz1cw1ixv.png)


### 步骤 6）配置 Postfix 邮件服务器


Postfix 的配置文件位于 `/etc/postfix/main.cf` 中。我们需要对配置文件进行一些修改，因此请使用你喜欢的文本编辑器将其打开：



```
# vi /etc/postfix/main.cf
```

更改以下几行：



```
myhostname = server1.crazytechgeek.info
mydomain = crazytechgeek.info
myorigin = $mydomain
## 取消注释并将 inet_interfaces 设置为 all##
inet_interfaces = all
## 更改为 all ##
inet_protocols = all
## 注释 ##
#mydestination = $myhostname, localhost.$mydomain, localhost
## 取消注释 ##
mydestination = $myhostname, localhost.$mydomain, localhost, $mydomain
## 取消注释并添加 IP 范围 ##
mynetworks = 192.168.1.0/24, 127.0.0.0/8
## 取消注释 ##
home_mailbox = Maildir/
```

完成后，保存并退出配置文件。重新启动 postfix 服务以使更改生效：



```
# systemctl restart postfix
```

### 步骤 7）测试 Postfix 邮件服务器


测试我们的配置是否有效，首先，创建一个测试用户。



```
# useradd postfixuser
# passwd postfixuser
```

接下来，运行以下命令，从本地用户 `pkumar` 发送邮件到另一个用户 `postfixuser`。



```
# telnet localhost smtp
或者
# telnet localhost 25
```

如果未安装 telnet 服务，那么可以使用以下命令进行安装：



```
# dnf install telnet -y
```

如前所述运行命令时，应获得如下输出：



```
[root@linuxtechi ~]# telnet localhost 25
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
220 server1.crazytechgeek.info ESMTP Postfix
```

上面的结果确认与 postfix 邮件服务器的连接正常。接下来，输入命令：



```
# ehlo localhost
```

输出看上去像这样：



```
250-server1.crazytechgeek.info
250-PIPELINING
250-SIZE 10240000
250-VRFY
250-ETRN
250-STARTTLS
250-ENHANCEDSTATUSCODES
250-8BITMIME
250-DSN
250 SMTPUTF8
```

接下来，运行橙色高亮的命令，例如 `mail from`、`rcpt to`、`data`，最后输入 `quit`：



```
mail from:<pkumar>
250 2.1.0 Ok
rcpt to:<postfixuser>
250 2.1.5 Ok
data
354 End data with <CR><LF>.<CR><LF>
Hello, Welcome to my mailserver (Postfix)
.
250 2.0.0 Ok: queued as B56BF1189BEC
quit
221 2.0.0 Bye
Connection closed by foreign host
```

完成 `telnet` 命令可从本地用户 `pkumar` 发送邮件到另一个本地用户 `postfixuser`，如下所示：


![Send-email-with-telnet-centos8](/data/attachment/album/201911/21/072901f78s7ht7bzmkk747.png)


如果一切都按计划进行，那么你应该可以在新用户的家目录中查看发送的邮件：



```
# ls /home/postfixuser/Maildir/new
1573580091.Vfd02I20050b8M635437.server1.crazytechgeek.info
#
```

要阅读邮件，只需使用 cat 命令，如下所示：



```
# cat /home/postfixuser/Maildir/new/1573580091.Vfd02I20050b8M635437.server1.crazytechgeek.info
```

![Read-postfix-email-linux](/data/attachment/album/201911/21/072903kpvvrg53bmcbmx5u.png)


### Postfix 邮件服务器日志


Postfix 邮件服务器邮件日志保存在文件 `/var/log/maillog` 中，使用以下命令查看实时日志，



```
# tail -f /var/log/maillog
```

![postfix-maillogs-centos8](/data/attachment/album/201911/21/072905l7zsofxsoocmxxpr.png)


### 保护 Postfix 邮件服务器


建议始终确保客户端和 Postfix 服务器之间的通信安全，这可以使用 SSL 证书来实现，它们可以来自受信任的权威机构或自签名证书。在本教程中，我们将使用 `openssl` 命令生成用于 Postfix 的自签名证书，


我假设 `openssl` 已经安装在你的系统上，如果未安装，请使用以下 `dnf` 命令：



```
# dnf install openssl -y
```

使用下面的 `openssl` 命令生成私钥和 CSR（证书签名请求）：



```
# openssl req -nodes -newkey rsa:2048 -keyout mail.key -out mail.csr
```

![Postfix-Key-CSR-CentOS8](/data/attachment/album/201911/21/072906uugozol5vr5rdsur.png)


现在，使用以下 openssl 命令生成自签名证书：



```
# openssl x509 -req -days 365 -in mail.csr -signkey mail.key -out mail.crt
Signature ok
subject=C = IN, ST = New Delhi, L = New Delhi, O = IT, OU = IT, CN = server1.crazytechgeek.info, emailAddress = root@linuxtechi
Getting Private key
#
```

现在将私钥和证书文件复制到 `/etc/postfix` 目录下：



```
# cp mail.key mail.crt /etc/postfix
```

在 Postfix 配置文件中更新私钥和证书文件的路径：



```
# vi /etc/postfix/main.cf
………
smtpd_use_tls = yes
smtpd_tls_cert_file = /etc/postfix/mail.crt
smtpd_tls_key_file = /etc/postfix/mail.key
smtpd_tls_security_level = may
………
```

重启 Postfix 服务以使上述更改生效：



```
# systemctl restart postfix
```

让我们尝试使用 `mailx` 客户端将邮件发送到内部本地域和外部域。


从 `pkumar` 发送内部本地邮件到 `postfixuser` 中：



```
# echo "test email" | mailx -s "Test email from Postfix MailServer" -r root@linuxtechi root@linuxtechi
```

使用以下命令检查并阅读邮件：



```
# cd /home/postfixuser/Maildir/new/
# ll
total 8
-rw-------. 1 postfixuser postfixuser 476 Nov 12 17:34 1573580091.Vfd02I20050b8M635437.server1.crazytechgeek.info
-rw-------. 1 postfixuser postfixuser 612 Nov 13 02:40 1573612845.Vfd02I20050bbM466643.server1.crazytechgeek.info
# cat 1573612845.Vfd02I20050bbM466643.server1.crazytechgeek.info
```

![Read-Postfixuser-Email-CentOS8](/data/attachment/album/201911/21/072908u11ytm69g69tdtfl.png)


从 `postfixuser` 发送邮件到外部域（`root@linuxtechi.com`）：



```
# echo "External Test email" | mailx -s "Postfix MailServer" -r root@linuxtechi root@linuxtechi
```

注意：如果你的 IP 没有被任何地方列入黑名单，那么你发送到外部域的邮件将被发送，否则它将被退回，并提示你的 IP 被 spamhaus 之类的数据库列入黑名单。


### 检查 Postfix 邮件队列


使用 `mailq` 命令列出队列中的邮件：



```
# mailq
Mail queue is empty
#
```

完成！我们的 Postfix 配置正常工作了！目前就这样了。我们希望你觉得本教程有见地，并且你可以轻松地设置本地 Postfix 服务器。




---


via: <https://www.linuxtechi.com/install-configure-postfix-mailserver-centos-8/>


作者：[James Kiarie](https://www.linuxtechi.com/author/james/) 选题：[lujun9972](https://github.com/lujun9972) 译者：[geekpi](https://github.com/geekpi) 校对：[wxy](https://github.com/wxy)


本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出


OK
**Postfix** is a free and opensource **MTA** (Mail Transfer Agent) used for routing or delivering emails on a Linux system. In this guide, you will learn how to install and configure Postfix on CentOS 8.

Lab set up:

- OS : CentOS 8 server
- IP Address : 192.168.1.13
- Hostname: server1.crazytechgeek.info (Ensure the domain name is pointed to the server’s IP)

#### Step 1) Update the system

The first step is to ensure that the system packages are up to date. To do so, update the system as follows:

# dnf update

Before proceeding further, also ensure that no other **MTAs** such as **Sendmail** are existing as this will cause conflict with Postfix configuration. To remove Sendmail, for example, run the command:

# dnf remove sendmail

#### Step 2) Set Hostname and update /etc/hosts file

Use below hostnamectl command to set the hostname on your system,

# hostnamectl set-hostname server1.crazytechgeek.info # exec bash

Additionally, you need to add the system’s hostname and IP entries in the /etc/hosts file

# vim /etc/hosts 192.168.1.13 server1.crazytechgeek.info

Save and exit the file.

**Read Also **: [How to Setup DNS Server (Bind) on CentOS 8 / RHEL8](https://www.linuxtechi.com/setup-bind-server-centos-8-rhel-8/)

#### Step 3) Install Postfix Mail Server

After verifying that no other MTA is running on the system install Postfix by executing the command:

# dnf install postfix

#### Step 4) Start and enable Postfix Service

Upon successful installation of Postfix, start and enable Postfix service by running:

# systemctl start postfix # systemctl enable postfix

To check Postfix status, run the following systemctl command

# systemctl status postfix

Great, we have verified that Postfix is up and running. Next, we are going to configure Postfix to send emails locally to our server.

#### Step 5) Install mailx email client

Before configuring the Postfix server, we need to install mailx feature, To install mailx, run the command:

# dnf install mailx

#### Step 6) Configure Postfix Mail Server


Postfix’s configuration file is located in **/etc/postfix/main.cf**. We need to make a few changes in the configuration file, so open it using your favorite text editor.

# vi /etc/postfix/main.cf

Make changes to the following lines:

myhostname = server1.crazytechgeek.info mydomain = crazytechgeek.info myorigin = $mydomain ## Uncomment and Set inet_interfaces to all ## inet_interfaces = all ## Change to all ## inet_protocols = all ## Comment ## #mydestination = $myhostname, localhost.$mydomain, localhost ##- Uncomment ## mydestination = $myhostname, localhost.$mydomain, localhost, $mydomain ## Uncomment and add IP range ## mynetworks = 192.168.1.0/24, 127.0.0.0/8 ## Uncomment ## home_mailbox = Maildir/

Once done, save and exit the configuration file. Restart postfix service for the changes to take effect

# systemctl restart postfix

#### Step 7) Testing Postfix Mail Server

Test whether our configuration is working, first, create a test user

# useradd postfixuser # passwd postfixuser

Next, run the command below to send email from **pkumar** local user to another user ‘**postfixuser**‘

# telnet localhost smtp or # telnet localhost 25

If telnet service is not installed, you can install it using the command:

# dnf install telnet -y

When you run the command as earlier indicated, you should get the output as shown

[root@server1 ~]# telnet localhost 25 Trying 127.0.0.1... Connected to localhost. Escape character is '^]'. 220 server1.crazytechgeek.info ESMTP Postfix

Above confirm that connectivity to postfix mail server is working fine. Next, type the command:

# ehlo localhost

Output will be something like this

250-server1.crazytechgeek.info 250-PIPELINING 250-SIZE 10240000 250-VRFY 250-ETRN 250-STARTTLS 250-ENHANCEDSTATUSCODES 250-8BITMIME 250-DSN 250 SMTPUTF8

Next, run the commands highlighted in orange, like “mail from”, “rcpt to”, data and then finally type quit,

mail from:<pkumar> 250 2.1.0 Ok rcpt to:<postfixuser> 250 2.1.5 Ok data 354 End data with <CR><LF>.<CR><LF> Hello, Welcome to my mailserver (Postfix) . 250 2.0.0 Ok: queued as B56BF1189BEC quit 221 2.0.0 Bye Connection closed by foreign host

Complete telnet command to send email from local user “**pkumar**” to another local user “**postfixuser**” would be something like below

If everything went according to plan, you should be able to view the email sent at the new user’s home directory.

# ls /home/postfixuser/Maildir/new 1573580091.Vfd02I20050b8M635437.server1.crazytechgeek.info #

To read the email, simply use the cat command as follows:

# cat /home/postfixuser/Maildir/new/1573580091.Vfd02I20050b8M635437.server1.crazytechgeek.info

#### Postfix mail server logs

Postfix mail server mail logs are stored in the file “**/var/log/maillog**“, use below command to view the live logs,

# tail -f /var/log/maillog

#### Securing Postfix Mail Server

It is always recommended secure the communication of between clients and postfix server, this can be achieved using SSL certificates, these certificates can be either from trusted authority or Self Signed Certificates. In this tutorial we will generate Self Signed certificated for postfix using **openssl** command,

I am assuming openssl is already installed on your system, in case it is not installed then use following dnf command,

# dnf install openssl -y

Generate Private key and CSR (Certificate Signing Request) using beneath openssl command,

# openssl req -nodes -newkey rsa:2048 -keyout mail.key -out mail.csr

Now Generate Self signed certificate using following openssl command,

# openssl x509 -req -days 365 -in mail.csr -signkey mail.key -out mail.crt Signature ok subject=C = IN, ST = New Delhi, L = New Delhi, O = IT, OU = IT, CN = server1.crazytechgeek.info, emailAddress =[[email protected]]Getting Private key #

Now copy private key and certificate file to /etc/postfix directory

# cp mail.key mail.crt /etc/postfix

Update Private key and Certificate file’s path in postfix configuration file,

# vi /etc/postfix/main.cf ……… smtpd_use_tls = yes smtpd_tls_cert_file = /etc/postfix/mail.crt smtpd_tls_key_file = /etc/postfix/mail.key smtpd_tls_security_level = may ………

Restart postfix service to make above changes into the effect.

# systemctl restart postfix

Let’s try to send email to internal local domain and external domain using mailx client.

**Sending local internal email from pkumar user to postfixuser**

# echo "test email" | mailx -s "Test email from Postfix MailServer" -r[[email protected]][[email protected]]

Check and read the email using the following,

# cd /home/postfixuser/Maildir/new/ # ll total 8 -rw-------. 1 postfixuser postfixuser 476 Nov 12 17:34 1573580091.Vfd02I20050b8M635437.server1.crazytechgeek.info -rw-------. 1 postfixuser postfixuser 612 Nov 13 02:40 1573612845.Vfd02I20050bbM466643.server1.crazytechgeek.info # cat 1573612845.Vfd02I20050bbM466643.server1.crazytechgeek.info

**Sending email from postfixuser to external domain ( [email protected])**

# echo "External Test email" | mailx -s "Postfix MailServer" -r[[email protected]][[email protected]]

**Note:** If Your IP is not blacklisted anywhere then your email to external domain will be delivered otherwise it will be bounced saying that IP is blacklisted in so and so spamhaus database.

#### Check Postfix mail queue

Use mailq command to list mails which are in queue.

# mailq Mail queue is empty #

And that’s it! Our Postfix configuration is working! That’s all for now. We hope you found this tutorial insightful and that you can comfortably set up your local Postfix server.

**Read Also**: [How to Install and Configure Samba on CentOS 8](https://www.linuxtechi.com/install-configure-samba-centos-8/)

**Read Also** : [How to Install Zimbra Mail Server on CentOS 8 / RHEL 8](https://www.linuxtechi.com/install-zimbra-mail-server-centos-8-rhel-8/)

BernardoHello, the local mail sending/receiving works all right for me, but when I try to send a message to my gmail account it bounces back, without saying much (like it would in the case you pointed out of blocked IPs).

If could please check out the log file and maybe point out what could be wrong from it I would greatly appreciate it!

Here is the log output:

‘https://pastebin.com/kshmHbVc’

Note: I’ve changed some usernames/domain names for privacy reasons

Pradeep KumarBy looking at the logs, it seems like issue with hostname of your mailserver. Did u update the hostname in /etc/hosts file and /etc/postfix/main.cf.

BrianThanks for your instruction.

I have received email in my Gmail, however, when I tried to reply, nothing came to my inbox. Can you give me some advice?

Pradeep KumarYou need to add MX record for your domain in DNS server to start receiving the emails from outside like Gmail, Yahoo etc

Kenny MaCould we connect to mail server with outlook after adding MX record?

Anything we need to do in server?

Pradeep KumarYes, You can configure your email id in outlook after adding MX record. MX record will route the emails from outside world to your mail server (postfix). For Sending emails locally & to outside world doesn’t need MX record.

AnindyaHi,

Thank you for this tutorial.

I am able to send email to my own domain’s email addresses but unable to send email to any other domain.

Can you please help me on this?

Thanks,

Anindya

Van TranBy default, Postfix uses port 25 for SMTP. For the sake of avoiding abuse for bad mail, most VPS service providers block this port. You can try the




`command telnet gmail-smtp-in.l.google.com 25`

, if you get a response likeTrying 74.125.68.26...

Connected to gmail-smtp-in.l.google.com.

Escape character is '^]'.

220 mx.google.com ESMTP m6si752389plx.46 - gsmtp

then you can use port 25 to send mail to external servers. Otherwise, you need to contact your service provider to ask them to open port 25. or configure Postfix to use a different port.