准备工作

1. 一台公网服务器（需要不被服务商限制发件收件的，也就是端口25、110、143、465、587、993、995不被限制），如有防火墙或安全组需要把这些端口开放

2. 一个域名，最好是com cn org的一级域名

3. 域名备案（如果服务器是国外的则不需要备案）

一、配置域名解析

1. 登录阿里云，找到云解析DNS

选择域名，如abc.com

①. 添加MX记录

- 记录类型：MX

- 主机记录：@

- 记录值：mail.abc.com

- MX优先级：1

②添加A记录

- 记录类型：A

- 主机记录：mail

- 记录值：服务器IP

- TTL：10分钟

③添加SPF记录

- 记录类型：TXT

- 主机记录：@

- 记录值：v=spf1 mx:mail.abc.com ip4:服务器IP -all

- TTL：10分钟

最后完成如下图

2. 安装并配置Postfix

apt-get update
sudo apt install -y postfix

安装过程中有选项需要选择，先选择1（No configuration），等下一步再单独配置

安装完成，输入下面命令配置Postfix

sudo dpkg-reconfigure postfix

将显示配置界面，选择 Internet Site ，然后分别输入或者选择以下值

•  mail.abc.com
• steve
• mail.abc.com, abc.com, localhost.localdomain, localhost
• no
• 127.0.0.0/8
• 0
• +
• ipv4

配置邮箱目录

sudo postconf -e 'home_mailbox = Maildir/'

使用 SASL（Dovecot SASL）配置 Postfix 的 SMTP-AUTH，在终端提示符下运行这些命令

sudo postconf -e 'smtpd_sasl_type = dovecot'
sudo postconf -e 'smtpd_sasl_path = private/auth'
sudo postconf -e 'smtpd_sasl_local_domain = $myhostname'
sudo postconf -e 'smtpd_sasl_security_options = noanonymous,noplaintext'
sudo postconf -e 'smtpd_sasl_tls_security_options = noanonymous'
sudo postconf -e 'broken_sasl_auth_clients = yes'
sudo postconf -e 'smtpd_sasl_auth_enable = yes'
sudo postconf -e 'smtpd_recipient_restrictions = permit_sasl_authenticated,permit_mynetworks,reject_unauth_destination'

配置TLS（使用自签名证书）

[root@mail ~]# cd
 
# 生成私钥
[root@mail ~]# openssl genrsa -des3 -out server.key 2048
Enter pass phrase:    #输入密码
Verifying - Enter pass phrase:  #重复输入密码
 
#下面这个步骤是删除server.key中的密码
[root@mail ~]# openssl rsa -in server.key -out server.key.insecure
Enter pass phrase for server.key:  #输入刚才设置的密码
writing RSA key

#重命名证书
[root@mail ~]# mv server.key server.key.secure
[root@mail ~]# mv server.key.insecure server.key

# 生成CSR（证书签名请求）
[root@mail ~]# openssl req -new -key server.key -out server.csr
Enter pass phrase for server.key: #输入刚才设置的密码
You are about to be asked to enter information that will be incorporated
into your certificate request.
What you are about to enter is what is called a Distinguished Name or a DN.
There are quite a few fields but you can leave some blank
For some fields there will be a default value,
If you enter '.', the field will be left blank.
-----
Country Name (2 letter code) [XX]:CN #国家简称
State or Province Name (full name) []:Beijing #省
Locality Name (eg, city) [Default City]:Beijing  #城市
Organization Name (eg, company) [Default Company Ltd]:OPS  #公司名
Organizational Unit Name (eg, section) []:OPS   #部门名
Common Name (eg, your name or your server's hostname) []:mail.abc.com
Email Address []:[email protected]  
Please enter the following 'extra' attributes
to be sent with your certificate request
A challenge password []:  #直接按Enter
An optional company name []:  #直接按Enter

#生成自签名证书
[root@mail ~]# openssl x509 -req -days 3650 -in server.csr -signkey server.key -out server.crt
Enter pass phrase for server.key:  #直接按Enter
Certificate request self-signature ok
subject=C = CN, ST = Beijing, L = Beijing, O = OPS, OU = OPS, CN = mail.abc.com, emailAddress = [email protected]
Getting Private key

#设置权限
[root@mail ~]# chmod 400 server.*

最后把证书拷贝到系统证书目录

sudo cp server.crt /etc/ssl/certs
sudo cp server.key /etc/ssl/private

拥有证书后，配置 Postfix，在终端提示符下运行这些命令：

sudo postconf -e 'smtp_tls_security_level = may'
sudo postconf -e 'smtpd_tls_security_level = may'
sudo postconf -e 'smtp_tls_note_starttls_offer = yes'
sudo postconf -e 'smtpd_tls_key_file = /etc/ssl/private/server.key'
sudo postconf -e 'smtpd_tls_cert_file = /etc/ssl/certs/server.crt'
sudo postconf -e 'smtpd_tls_loglevel = 1'
sudo postconf -e 'smtpd_tls_received_header = yes'
sudo postconf -e 'smtpd_tls_auth_only = yes'

最后查看配置 vim /etc/postfix/main.cf 后面部分如下即可

# TLS parameters
smtpd_tls_cert_file = /etc/ssl/certs/server.crt
smtpd_tls_key_file = /etc/ssl/private/server.key
smtpd_tls_security_level = may

smtp_tls_CApath=/etc/ssl/certs
smtp_tls_security_level = may
smtp_tls_session_cache_database = btree:${data_directory}/smtp_scache


smtpd_relay_restrictions = permit_mynetworks permit_sasl_authenticated defer_unauth_destination
myhostname = mail.abc.com
alias_maps = hash:/etc/aliases
alias_database = hash:/etc/aliases
myorigin = /etc/mailname
mydestination = mail.abc.com, abc.com, localhost.localdomain, localhost
relayhost =
mynetworks = 127.0.0.0/8
mailbox_size_limit = 0
recipient_delimiter = +
inet_interfaces = all
inet_protocols = ipv4
home_mailbox = Maildir/
smtpd_sasl_type = dovecot
smtpd_sasl_path = private/auth
smtpd_sasl_local_domain = $myhostname
smtpd_sasl_security_options = noanonymous,noplaintext
smtpd_sasl_tls_security_options = noanonymous
broken_sasl_auth_clients = yes
smtpd_sasl_auth_enable = yes
smtpd_recipient_restrictions = permit_sasl_authenticated,permit_mynetworks,reject_unauth_destination
smtp_tls_note_starttls_offer = yes
smtpd_tls_loglevel = 1
smtpd_tls_received_header = yes
smtpd_tls_auth_only = yes

配置SMTPS ==> vim /etc/postfix/master.cf 

smtps部分去掉注释

smtps     inet  n       -       -       -       -       smtpd
  -o smtpd_tls_wrappermode=yes
  -o smtpd_sasl_auth_enable=yes
  -o smtpd_client_restrictions=permit_sasl_authenticated,reject
  -o milter_macro_daemon_name=ORIGINATING

3. 安装并配置Dovecot

sudo apt install -y dovecot-core dovecot-imapd dovecot-pop3d

 安装完成配置信息

vim /etc/dovecot/conf.d/10-auth.conf

auth_mechanisms = plain  改成  auth_mechanisms = plain login 

vim /etc/dovecot/conf.d/10-master.conf
改成如下
service auth {
  # auth_socket_path points to this userdb socket by default. It's typically
  # used by dovecot-lda, doveadm, possibly imap process, etc. Its default
  # permissions make it readable only by root, but you may need to relax these
  # permissions. Users that have access to this socket are able to get a list
  # of all usernames and get results of everyone's userdb lookups.
  unix_listener auth-userdb {
    #mode = 0600
    #user = 
    #group = 
  }
    
  # Postfix smtp-auth
  unix_listener /var/spool/postfix/private/auth {
    mode = 0660
    user = postfix
    group = postfix
  }
 }

vim /etc/dovecot/dovecot.conf

listen = *, ::

#!include conf.d/*.conf

!include conf.d/10-auth.conf
!include conf.d/10-master.conf

ssl = no
disable_plaintext_auth = no
mail_location = maildir:~/Maildir

4. 启动邮箱服务并新增邮箱用户

sudo systemctl start postfix
sudo systemctl start dovecot
#重启命令：
sudo systemctl restart postfix
sudo systemctl restart dovecot

#======新建邮箱用户======
useradd -m 用户名
passwd 用户名
#输入密码
#确认密码

#======验证账户======
sudo doveadm auth test 用户名

5. 安装mailutils测试发件

sudo apt install -y mailutils

#======测试发件======
echo '搭建邮件服务器成功啦！！！' | mail -s '通知！' [email protected]

6. 安装系统日志

sudo yum install -y rsyslog
sudo systemctl enable rsyslog
sudo systemctl start rsyslog
后续查看邮件服务日志方式
sudo tail -f /var/log/maillog

二、使用Foxmail收发邮件

①windows10版本的Foxmail 新建账号完成后闪退，所以先设置下：

首先找到Foxmail快捷方式，右键属性。
找到兼容性，并且在下方找到“以管理员身份运行此程序”，勾选，确定

②打开Foxmail，新建账号 => 其它邮箱 => 手动设置 => POP3

邮件账号：账号@abc.com

密码：xxxxxx

POP服务器：mail.abc.com　　  SSL 110（不勾选，如果想勾选走995端口，则需要配置Dovecot的SSL信息，可自行研究）

SMTP服务器：mail.abc.com　　SSL 465（勾选）

 注：虽然发件服务(SMTP)启用了SSL走的端口是465，但是实测25端口还得开放，不然无法接收外部邮件

参考：https://ubuntu.com/server/docs/install-and-configure-postfix#smtps