邮件传输过程中主要有MTA,MUA,MAA,MDA

  MUA：邮件用户代理（Mail User Agent），指的是客户端程序，如outlook,foxmail,thunderbird

  MTA：邮件传输代理（Mail Transfer Agent），指dovecot软件提供的pop3,imap等收信服务

  MDA：邮件过滤代理（Mail Delivery Agent），主要有procmail等

   Sendmail常规服务器配置流程：

  （1）配置sendmail.mc文件

  （2）使用m4工具将sendmail.mc文件导入sendmail.cf文件

  （3）配置local-host-names文件

  （4）建立用户帐号

  （5）重新启动服务使配置生效

   在配置sendmail之前，需要设置并搭建DNS服务器。

  [root@localhost /]# nslookup 
  > set type=mx
  > gd2010.com.
  Server:          172.26.39.23
  Address:        172.26.39.23#53

  gd2010.com      mail exchanger = 10 mail.gd2010.com.

  实验目的：实现域内发送/接收邮件

  RHEL5默认安装sendmail-8.13.8-2.el5及m4-1.4.5-3.el5.1，只需要安装sendmail-cf-8.13.8-2.el5宏文件包

  [root@localhost Server]# rpm -ivh sendmail-cf-8.13.8-2.el5.i386.rpm #安装sendmail-cf包，提供主要的模板

  1）修改 /etc/mail/sendmail.mc第116行将smtp侦听范围从127.0.0.1改为0.0.0.0，否则邮件服务器无法正常发送邮件

  #出于安全考虑，默认只对lo回环网络接口(IP地址为127.0.0.1)提供服务，为了使服务器能够为主机的所有网络接口(地址为0.0.0.0)提供服务，开启sendmail服务器的网络接口

  2）修改第155行修改成域名：LOCAL_DOMAIN(`gd2010.com')dnl

  3）使用m4宏生成半二进制的配置文件 m4 /etc/mail/sendmail.mc > /etc/mail/sendmail.cf

  4）修改/etc/mail/local-host-names 文件添加域名和主机名

  [root@localhost Server]# cat >>/etc/mail/local-host-names<<EOF

  > gd2010.com.

  > mail.gd2010.com.

  > EOF

  5）如果需要使用POP3和IMAP协议接收邮件需要安装dovecot软件包

  安装dovecot软件包要解决其依赖性

  [root@localhost Server]# rpm -ivh perl-DBI-1.52-1.fc6.i386.rpm

  [root@localhost Server]# rpm -ivh mysql-5.0.22-2.1.i386.rpm

  [root@localhost Server]# rpm -ivh postgresql-libs-8.1.11-1.el5_1.1.i386.rpm # 解决libpq.so.4

  [root@localhost Server]# rpm -ivh dovecot-1.0-1.2.rc15.el5.i386.rpm

===========================================================================

  可以架设YUM本地服务器实现解决依赖性自动化安装

  [root@localhost ~]# mkdir -p /media/yum

  [root@localhost ~]# mount /dev/cdrom /media/yum/

  mount: block device /dev/cdrom is write-protected, mounting read-only

  [root@localhost ~]# cd /media/yum/Server/

  [root@localhost Server]# rpm -ivh createrepo-0.4.4-2.fc6.noarch.rpm

  [root@localhost Server]# cd /media/

  [root@localhost media]# createrepo .

  [root@localhost media]# cat >/etc/yum.repos.d/server.repo<<EOF

  > [yum]

  > baseurl=file:///media

  > enabled=1

  > EOF

===========================================================================

  [root@localhost Server]# /etc/init.d/sendmail restart

  [root@localhost Server]# /etc/init.d/dovecot restart

  [root@localhost Server]# netstat –ntla #使用netstat命令测试是否开启SMTP的25端口、POP3的110端口及IMAP的143端口

  Active Internet connections (servers and established)

  Proto Recv-Q Send-Q Local      Address            Foreign Address           State        

  tcp        0      0 0.0.0.0:111            0.0.0.0:*                 LISTEN     

  tcp        0      0 127.0.0.1:631        0.0.0.0:*                 LISTEN     

  tcp        0      0 0.0.0.0:25              0.0.0.0:*                 LISTEN     

  tcp        0      0 0.0.0.0:795            0.0.0.0:*                 LISTEN     

  tcp        0      0 :::993                      :::*                        LISTEN     

  tcp        0      0 :::995                      :::*                        LISTEN     

  tcp        0      0 :::110                      :::*                        LISTEN     

  tcp        0      0 :::143                      :::*                        LISTEN     

  tcp        0      0 :::22                      :::*                        LISTEN     

  [root@localhost Server]# telnet localhost 25 #验证Sendmail的SMTP认证功能

  Trying 127.0.0.1...

  Connected to localhost.localdomain (127.0.0.1).

  Escape character is '^]'.

  220 localhost.localdomain ESMTP Sendmail 8.13.8/8.13.8; Thu, 2 Sep 2010 21:09:54 -0700

  ehlo localhost #验证Sendmail的SMTP认证功能

  250-localhost.localdomain Hello localhost.localdomain [127.0.0.1], pleased to meet you

  250-ENHANCEDSTATUSCODES

  250-PIPELINING

  250-8BITMIME

  250-SIZE

  250-DSN

  250-ETRN

  250-DELIVERBY

  250 HELP

  quit

  221 2.0.0 localhost.localdomain closing connection

  Connection closed by foreign host.

===========================================================================

  [root@localhost Server]# telnet localhost 110

  Trying 127.0.0.1...

  Connected to localhost.localdomain (127.0.0.1).

  Escape character is '^]'.

  +OK Dovecot ready.

===========================================================================

  创建用户账号

  注：sendmail服务器使用linux系统中的用户账号作为邮件账号，因此为用户添加邮件账号只需要添加linux用户账号即可。为了便于对邮件用户进行管理，由于邮件账号通常不需要登录linux系统，因此可以在adduser命令使用“-s”选项指定用户的shell为“/sbin/nologin”，即不允许用户登录linux系统。在建立邮件用户账号之后，需要使用passwd命令为用户设置口令，以便用户发送和收取邮件时进行身份认证。

  [root@localhost Server]# useradd user1

  [root@localhost Server]# useradd user2

  [root@localhost Server]# su user1

  [user1@localhost Server]$ mail -vs "what is the weather like today?" user2@gd2010.com

  do you know ? i love you

  .

  Cc:

  user2@gd2010.com... Connecting to [127.0.0.1] via relay...

  220 localhost.localdomain ESMTP Sendmail 8.13.8/8.13.8; Fri, 3 Sep 2010 05:32:24 -0700

  >>> EHLO localhost.localdomain

  250-localhost.localdomain Hello localhost.localdomain [127.0.0.1], pleased to meet you

  250-ENHANCEDSTATUSCODES

  250-PIPELINING

  250-8BITMIME

  250-SIZE

  250-DSN

  250-ETRN

  250-DELIVERBY

  250 HELP

  >>> MAIL From:<user1@localhost.localdomain> SIZE=103

  250 2.1.0 <user1@localhost.localdomain>... Sender ok

  >>> RCPT To:<user2@gd2010.com>

  >>> DATA

  250 2.1.5 <user2@gd2010.com>... Recipient ok

  354 Enter mail, end with "." on a line by itself

  >>> .

  250 2.0.0 o83CWOAA010249 Message accepted for delivery

  user2@gd2010.com... Sent (o83CWOAA010249 Message accepted for delivery)

  Closing connection to [127.0.0.1]

  >>> QUIT

  221 2.0.0 localhost.localdomain closing connection

===========================================================================

  [user1@localhost Server]$ su user2

  Password:

  [user2@localhost Server]$ cat /var/spool/mail/user2

  From user1@localhost.localdomain  Fri Sep  3 05:32:24 2010

  Return-Path: <user1@localhost.localdomain>

  Received: from localhost.localdomain (localhost.localdomain [127.0.0.1])

        by localhost.localdomain (8.13.8/8.13.8) with ESMTP id o83CWOAA010249

        for <user2@gd2010.com>; Fri, 3 Sep 2010 05:32:24 -0700

  Received: (from user1@localhost)

        by localhost.localdomain (8.13.8/8.13.8/Submit) id o83CWONV010248

        for user2@gd2010.com; Fri, 3 Sep 2010 05:32:24 -0700

  Date: Fri, 3 Sep 2010 05:32:24 -0700

  From: user1@localhost.localdomain

  Message-Id: <201009031232.o83CWONV010248@localhost.localdomain>

  To: user2@gd2010.com

  Subject: what is the weather like today?

 

  do you know ? i love you

===========================================================================

  [root@localhost Server]# cat /var/log/maillog

  #所有信息都存储在这个日志文件中，包括用户名，主机名，出错代码。这些出错代码很有用处，可以通过这些让你对自己有更好的了解

 

  Sep  3 05:32:24 localhost sendmail[10248]: o83CWONV010248: from=user1, size=103, class=0,   nrcpts=1,   msgid=<201009031232.o83CWONV010248@localhost.localdomain>, relay=user1@localhost

  Sep  3 05:32:24 localhost sendmail[10249]: o83CWOAA010249: from=<user1@localhost.localdomain>, size=392, class=0,   nrcpts=1, msgid=<201009031232.o83CWONV010248@localhost.localdomain>, proto=ESMTP, daemon=MTA, relay=localhost.localdomain [127.0.0.1]

  Sep  3 05:32:24 localhost sendmail[10248]: o83CWONV010248: to=user2@gd2010.com, ctladdr=user1 (501/501), delay=00:00:00,   xdelay=00:00:00, mailer=relay, pri=30103, relay=[127.0.0.1] [127.0.0.1], dsn=2.0.0, stat=Sent (o83CWOAA010249 Message accepted for delivery)

  Sep  3 05:32:24 localhost sendmail[10250]: o83CWOAA010249: to=<user2@gd2010.com>,   ctladdr=<user1@localhost.localdomain> (501/501), delay=00:00:00, xdelay=00:00:00, mailer=local, pri=30602, dsn=2.0.0, stat=Sent