postfix 邮件服务器

服务端：

1. 卸载 sendmail：
   yum -y remove sendmail
2. 安装软件：
   yum -y install postfix dovecot cyrus-sasl-* mailx
   3 配置 postfix：
   vim /etc/postfix/main.cf

   queue_directory = /var/spool/postfix
   command_directory = /usr/sbin
   daemon_directory = /usr/libexec/postfix
   data_directory = /var/lib/postfix
   mail_owner = postfix
   myhostname = mail.xxxxx.com         #这里要换成你自己的邮箱服务器
   mydomain = xxxxx.com                #这里换成你自己的主机服务器
   myorigin = $mydomain
   inet_interfaces = all
   inet_protocols = ipv4
   mydestination = $myhostname, localhost.$mydomain, localhost,$mydomain,mail.$mydomain,www.$mydomain, ftp.$mydomain
   local_recipient_maps =
   unknown_local_recipient_reject_code = 550
   mynetworks = 0.0.0.0/0
   relay_domains = $mydestination
   alias_maps = hash:/etc/aliases
   alias_database = hash:/etc/aliases
   home_mailbox = Maildir/
   smtpd_banner = $myhostname ESMTP
   debug_peer_level = 2
   debugger_command =
   PATH=/bin:/usr/bin:/usr/local/bin:/usr/X11R6/bin
   ddd $daemon_directory/$process_name $process_id & sleep 5
   sendmail_path = /usr/sbin/sendmail.postfix
   newaliases_path = /usr/bin/newaliases.postfix
   mailq_path = /usr/bin/mailq.postfix
   setgid_group = postdrop
   html_directory = no
   manpage_directory = /usr/share/man
   sample_directory = /usr/share/doc/postfix-2.10.1/samples
   readme_directory = /usr/share/doc/postfix-2.10.1/README_FILES
   smtpd_sasl_auth_enable = yes
   smtpd_sasl_security_options = noanonymous
   broken_sasl_auth_clients = yes
   smtpd_recipient_restrictions = permit_sasl_authenticated,reject_unauth_destination,permit_mynetworks
   smtpd_client_restrictions = permit_sasl_authenticated

3. 配置 dovecot：
   1. 配置监听协议：
      vim /etc/dovecot/dovecot.conf

       protocols = imap pop3 lmtp
       listen = *
       dict {
       }
       !include conf.d/*.conf
       !include_try local.conf

   2. 配置登录方式：
      vim /etc/dovecot/conf.d/10-auth.conf

      disable_plaintext_auth = no
      auth_mechanisms = plain login
      !include auth-system.conf.ext

   3. 配置邮件存储位置：
      vim /etc/dovecot/conf.d/10-mail.conf

       mail_location = maildir:~/Maildir
       namespace inbox {
       inbox = yes
       }
       first_valid_uid = 1000
       mbox_write_locks = fcntl

   4. 配置 ssl（关闭）：
      vim /etc/dovecot/conf.d/10-ssl.conf

      ssl = no
      ssl_cert = </etc/pki/dovecot/certs/dovecot.pem
      ssl_key = </etc/pki/dovecot/private/dovecot.pem

4. 配置 sasl2：
   1. 配置系统认证：
      vim /etc/sysconfig/saslauthd

      SOCKETDIR=/run/saslauthd
      MECH=shadow
      FLAGS=

   2. 配置登录方式（创建新文件）：
      vim /usr/lib64/sasl2/smtpd.conf

      pwcheck_method: saslauthd
      mech_list: PLAIN LOGIN
      log_level:3

5. 添加用户：

   useradd  test_user
   passwd  test_user

6. 启动服务：

   systemctl  start  dovecot
   systemctl  start  postfix
   systemctl  start  saslauthd

7. 配置 mailx：
   vim /etc/mail.rc

   set append
   set ask
   set crt
   set dot
   set keep
   set emptybox
   set indentprefix="> "
   set quote
   set sendcharsets=iso-8859-1,utf-8
   set showname
   set showto
   set newmail=nopoll
   set autocollapse
   set markanswered
   ignore received in-reply-to message-id references
   ignore mime-version content-transfer-encoding
   fwdretain subject date from to
   set bsdcompat
   set from=test_user@xxxxx.com
   set smtp=mail.xxxxx.com
   set smtp-auth-user=test_user
   set smtp-auth-password=test_pass
   set smtp-auth=login

8. 发送邮件：

   echo  "内容"  |  mail  -s  "标题"  test@gmail.com
   或
   mail  -s  "标题"  test@gmail.com  <  test.txt

9. 查看发送日志：
   tail /var/log/maillog

客户端：

1. 安装 telnet：
   yum -y install telnet
2. 登录（ dovecot 的默认端口是110）：
   telnet xx.xx.xx.xx 110
   
3. 命令介绍：

   USER  xxx：输入用户名
   PASS  xxx：输入密码
   LIST：显示信箱
   RETR n：打开第n封信

4. 退出 telnet：

   ctl+]
   quit