apt-get update
sudo apt install -y postfix

sudo dpkg-reconfigure postfix

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

sudo postconf -e 'home_mailbox = Maildir/'

sudo postconf -e 'smtpd_sasl_type = dovecot'
sudo postconf -e 'smtpd_sasl_path = private/auth'
sudo postconf -e 'myhostname = mail.abc.com'
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'

[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.*

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

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'

# 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

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

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

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

sudo systemctl start postfix
sudo systemctl start dovecot
#重启命令：
sudo systemctl restart postfix
sudo systemctl restart dovecot
#设置开机自启动
sudo systemctl enable postfix
sudo systemctl enable 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

sudo apt install -y mailutils

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

sudo apt-get install -y rsyslog
sudo systemctl enable rsyslog
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/mail.log

vim /etc/dovecot/dovecot.conf

====================
#!include conf.d/*.conf
改成
!include conf.d/*.conf
====================
!include conf.d/10-auth.conf
!include conf.d/10-master.conf
ssl = no
改成
#!include conf.d/10-auth.conf
#!include conf.d/10-master.conf
#ssl = no
====================

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
====================
ssl_client_ca_dir = /etc/ssl/certs
改成
#ssl_client_ca_dir = /etc/ssl/certs
====================

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

====================
  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
  }
}
====================

netstat -lntp
#显示如下
xxxxxx    PID/Program name
xxxxxx     xxx/dovecot
#杀掉进程
kill -9 PID
#启动Dovecot
systemctl start dovecot