yum update -y
yum -y install postfix dovecot  cyrus-sasl

[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 []:admin@abc.com  
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 = admin@abc.com
Getting Private key

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

# 创建目录
mkdir -p /etc/ssl/private/
# 拷贝
sudo cp server.crt /etc/ssl/certs
sudo cp server.key /etc/ssl/private

vim /etc/postfix/main.cf

# 修改以下项，注释的解开，不要有重复项
# 设置为 mail.域名
myhostname = mail.abc.com
# 设置为 域名
mydomain = abc.com
# 往外发邮件的邮件域
myorigin = $mydomain
#监听的网卡
inet_interfaces = all
inet_protocols = ipv4
#服务的对象
mydestination = $myhostname, $mydomain, localhost.$mydomain, localhost
#邮件存放的目录
home_mailbox = Maildir/
 
# 新添加以下配置
#--------自定义（下面可以复制粘贴到文件最后面，用于设置服务器验为主，第一行设置发送附件大小）
#message_size_limit = 100000
smtpd_sasl_auth_enable = yes
smtpd_sasl_security_options = noanonymous,noplaintext
mynetworks = 127.0.0.0/8
smtpd_recipient_restrictions = permit_mynetworks,permit_sasl_authenticated,reject_unauth_destination

smtpd_sasl_type = dovecot
smtpd_sasl_path = private/auth
smtpd_sasl_local_domain = $myhostname
smtpd_sasl_tls_security_options = noanonymous
broken_sasl_auth_clients = yes

relayhost =
smtpd_relay_restrictions = permit_mynetworks permit_sasl_authenticated defer_unauth_destination
smtpd_use_tls = yes
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_note_starttls_offer = yes
smtpd_tls_loglevel = 1
smtpd_tls_received_header = yes
smtpd_tls_auth_only = yes

vim /etc/postfix/master.cf

# 分别把下列配置前面的#去掉
smtps     inet  n       -       n       -       -       smtpd
  -o smtpd_tls_wrappermode=yes
  -o smtpd_sasl_auth_enable=yes
  -o smtpd_recipient_restrictions=permit_sasl_authenticated,reject
  -o milter_macro_daemon_name=ORIGINATING

vim /etc/dovecot/dovecot.conf

# 注释的解开注释，不要有重复项
protocols = imap pop3 lmtp
listen = *, ::
 
# 以下内容添加到文件最后
mail_location = maildir:~/Maildir

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

# 设置mail_location为
mail_location = maildir:~/Maildir

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

====================
ssl_cert = </etc/dovecot/private/dovecot.pem
ssl_key = </etc/dovecot/private/dovecot.key
改成
ssl_cert = </etc/ssl/certs/server.crt
ssl_key = </etc/ssl/private/server.key
====================

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

====================
  # Postfix smtp-auth
  unix_listener /var/spool/postfix/private/auth {
    mode = 0660
    user = postfix
    group = postfix
  }

====================
  inet_listener imap {
    #port = 143
  }
改成
  inet_listener imap {
    #port = 143
    port = 0
  }
====================
service pop3-login {
  inet_listener pop3 {
    #port = 110
  }
}
改成
service pop3-login {
  inet_listener pop3 {
    #port = 110
    port = 0
  }
}
====================

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

auth_mechanisms = plain  改成  auth_mechanisms = plain login

vim /usr/lib/systemd/system/dovecot.service

# Type=forking后添加
ExecStartPost=/bin/sh -c 'chown root:dovecot /var/run/dovecot/master.pid'

# 加载系统服务
systemctl daemon-reload

sudo yum install -y rsyslog
# 设置开机自启动
sudo systemctl enable rsyslog
# 启动
sudo systemctl start rsyslog

#后续查看邮件服务日志方式（需要重启postfix和dovecot）
tail -f /var/log/maillog

#启动
sudo systemctl start postfix
sudo systemctl start dovecot

#设置开机自启动
sudo systemctl enable postfix
sudo systemctl enable dovecot

sudo yum install -y mailx

#======测试发件======
echo '搭建邮件服务器成功啦！！！' | mail -s '通知！' xxx@qq.com

useradd -m 用户名
passwd 用户名
# 输入密码
# 确认密码

sudo doveadm auth test 用户名