sendmail在企业网络中的应用

网友投稿 649 2022-09-23

sendmail在企业网络中的应用

一、本机客户端之间发送邮件

1、管理员身份给用户发邮件

[root@node1 ~]# service sendmail status sendmail (pid 2844) is running... //为了方便通知用户收到邮件，系统默认已经安装 [root@node1 ~]# chkconfig --list |grep sendmail sendmail 0:off 1:off 2:on 3:on 4:on 5:on 6:off //默认设置开机启动

[root@node1 ~]# set |less

[root@node1 ~]# cd /var/spool/mail/ //切换到邮箱目录下

[root@node1 mail]# useradd user1 //增加一个账号 [root@node1 mail]# ll

[root@node1 mail]# mail -s hello user1 //给user1发送一个标题为hello的邮件 hehe //邮件内容 . Cc: //此处可以添加多个用户的账号，进行超送

[root@node1 mail]# su – user1 //切换到user1用户

[user1@node1 ~]$ mail //查看邮件

[user1@node1 ~]$ mail //再次访问邮箱 No mail for user1 //邮箱已无邮件

注：读取过后的邮件如果用q退出邮箱，系统自动保存在mbox中，如果想继续保存在邮箱中，可用x退出

[root@node1 ~]# netstat -tupln |less //查看端口状态

tcp 0 0 127.0.0.1:25 0.0.0.0:* LISTEN 2844/sendmail: acce //sendmail在127.0.0.1 的25端口处于监听状态

2、使用telnet发邮件

[root@node1 ~]# telnet 127.0.0.1 25 // Trying 127.0.0.1... Connected to node1.a.com (127.0.0.1). Escape character is '^]'. 220 node1.a.com ESMTP Sendmail 8.13.8/8.13.8; Mon, 10 Sep 2012 11:26:53 +0800 help 214-2.0.0 This is sendmail 214-2.0.0 Topics: 214-2.0.0 HELO EHLO MAIL RCPT DATA 214-2.0.0 RSET NOOP QUIT HELP VRFY 214-2.0.0 EXPN VERB ETRN DSN AUTH 214-2.0.0 STARTTLS 214-2.0.0 For more info use "HELP ". 214-2.0.0 To report bugs in the implementation see 214-2.0.0 214-2.0.0 For local information send email to Postmaster at your site. 214 2.0.0 End of HELP info

HELO 127.0.0.1 //向127.0.0.1打招呼 250 node1.a.com Hello node1.a.com [127.0.0.1], pleased to meet you //127.0.0.1 做出回应

EHLO 127.0.0.1 250-node1.a.com Hello node1.a.com [127.0.0.1], pleased to meet you 250-ENHANCEDSTATUSCODES 250-PIPELINING 250-8BITMIME 250-SIZE 250-DSN 250-ETRN 250-DELIVERBY 250 HELP //EHLO下有很多扩展选项，这点与HELO有区别

HELP mail //mail的用法 214-2.0.0 MAIL From: [ ] //指明发送者 214-2.0.0 Specifies the sender. Parameters are ESMTP extensions. 214-2.0.0 See "HELP DSN" for details. 214 2.0.0 End of HELP info

mail from:root@localhost //发送人的地址 250 2.1.0 root@localhost... Sender ok //发送者 HELP RCPT //RCPT的用法 214-2.0.0 RCPT To: [ ] //指明接收者 214-2.0.0 Specifies the recipient. Can be used any number of times. 214-2.0.0 Parameters are ESMTP extensions. See "HELP DSN" for details. 214 2.0.0 End of HELP info RCPT to:user1@localhost //接受人的地址 250 2.1.5 user1@localhost... Recipient ok //接收者

DATA //写信件前，此步一定不可少 354 Enter mail, end with "." on a line by itself subject:hello1 //信件标题 I am very happy! //信件内容 . //信件以"."结束 250 2.0.0 q8A3ve9T029282 Message accepted for delivery

quit

[root@node1 ~]# su – user1 //切换到user1用户下 [user1@node1 ~]$ mail

二、外部telnet到本机发送邮件

1、从外部客户机telnet到本地主机

注：因为sendmail监听的是127.0.0.1，而127.0.0.1是一个封闭地址，只能实现本机内部进程之间的通信，外部主机无法与其进行通信

下面对sendmail进行一些改动

2、修改文件

[root@node1 ~]# cd /etc/mail

[root@node1 mail]# ll

3、安装sendmail及其他工具

[root@node1 mail]# rpm -qa |grep sendmail sendmail-8.13.8-2.el5 [root@node1 mail]# mkdir /mnt/cdrom //建立光盘挂载点 [root@node1 mail]# mount /dev/cdrom /mnt/cdrom/ //挂载光盘 mount: block device /dev/cdrom is write-protected, mounting read-only [root@node1 mail]# cd /mnt/cdrom/Server/ [root@node1 Server]# ll sendm* //编辑mc文件必须安装cf文件

[root@node1 Server]# ll m4* //m4工具可将mc文件转换成cf文件，此处m4工具已安装

[root@node1 Server]# rpm -ivh sendmail-cf-8.13.8-2.el5.i386.rpm //安装cf文件 Preparing... ########################################### [100%] 1:sendmail-cf ########################################### [100%]

[root@node1 mail]# vim sendmail.mc

[root@node1 mail]# service sendmail restart //重启服务

[root@node1 mail]# netstat -tupln |grep sendmail //查看端口 tcp 0 0 0.0.0.0:25 0.0.0.0:* LISTEN 29739/sendmail: acc

4、再次从外部telnet到192.168.101.5 25

可以进入！

5、从外部客户机给本地用户发邮件

[root@node1 ~]# su – user1 //切换到user1 [user1@node1 ~]$ mail

[root@node1 ~]# netstat -tupln |grep sendmail //查看端口 tcp 0 0 0.0.0.0:25 0.0.0.0:* LISTEN 29739/sendmail: acc

三、中继的实现

[root@node1 mail]# service sendmail restart

四、案例搭建两台服务器使其互相通信

实验拓扑图

1、163.com的搭建

（1）、修改主机名

（2）、安装dns服务器

[root@node1 ~]# mkdir /mnt/cdrom //建立光盘挂载点 [root@node1 ~]# mount /dev/cdrom /mnt/cdrom/ //挂载光盘 mount: block device /dev/cdrom is write-protected, mounting read-only [root@node1 ~]# cd /mnt/cdrom/Server/

[root@node1 Server]# rpm -ivh bind-9.3.6-4.P1.el5.i386.rpm Preparing... ########################################### [100%] package bind-9.3.6-4.P1.el5.i386 is already installed [root@node1 Server]# rpm -ivh bind-chroot-9.3.6-4.P1.el5.i386.rpm Preparing... ########################################### [100%] package bind-chroot-9.3.6-4.P1.el5.i386 is already installed [root@node1 Server]# rpm -ivh caching-nameserver-9.3.6-4.P1.el5.i386.rpm Preparing... ########################################### [100%] package caching-nameserver-9.3.6-4.P1.el5.i386 is already installed

（3）、拷贝并生成文件

[root@node1 Server]# cd /var/named/chroot/etc/

[root@node1 etc]# ll

[root@node1 etc]# cp -p named.caching-nameserver.conf named.conf //拷贝并生成文件

[root@node1 etc]# ll

[root@node1 etc]# vim named.conf //编辑此文件

[root@node1 etc]# vim named.rfc1912.zones

[root@node1 etc]# cd ../var/named/ [root@node1 named]# ll

[root@node1 named]# cp -p localhost.zone 163.com.zone //拷贝生成163.com.zone

[root@node1 named]# ll

[root@node1 named]# vim 163.com.zone //编辑163.com.zone

[root@node1 named]# service named start //启动dns服务 Starting named: [ OK ]

[root@node1 named]# chkconfig named //设置为开机时启动

[root@node1 named]# vim /etc/resolv.conf

[root@node1 named]# init 6

[root@mail mail]# vim sendmail.mc

[root@mail mail]# vim access

[root@mail mail]# vim local-host-names

[root@mail mail]# service sendmail restart

[root@mail mail]# useradd user2

[root@mail mail]# useradd user3

[root@mail mail]# cd /var/spool/mail/

[root@mail mail]# ll

[root@mail ~]# mail -s hello user2 hello! ，， . Cc: [root@mail ~]# su - user2 [user2@mail ~]$ mail Mail version 8.1 6/6/93. Type ? for help. "/var/spool/mail/user2": 1 message 1 new >N 1 root@mail.163.com Tue Sep 11 16:05 17/577 "hello" & 1 Message 1: From root@mail.163.com Tue Sep 11 16:05:08 2012 Date: Tue, 11 Sep 2012 16:05:08 +0800 From: root To: user2@mail.163.com Subject: hello

hello! ，，

& q Saved 1 message in mbox

[root@mail ~]# cd /mnt/cdrom/Server/ [root@mail Server]# ll dov*

[root@mail Server]# rpm -ivh dovecot-1.0.7-7.el5.i386.rpm Preparing... ########################################### [100%] 1:dovecot ########################################### [100%]

[root@mail Server]# service dovecot start Starting Dovecot Imap: [ OK ] [root@mail Server]# chkconfig dovecot on [root@mail Server]# netstat -tupln |less

[root@mail Server]# passwd user2 Changing password for user user2. New UNIX password: BAD PASSWORD: it is WAY too short Retype new UNIX password: passwd: all authentication tokens updated successfully. [root@mail Server]# passwd user3 Changing password for user user3. New UNIX password: BAD PASSWORD: it is WAY too short Retype new UNIX password: passwd: all authentication tokens updated successfully.

[root@mail Server]# vim /etc/aliases

[root@mail Server]# service sendmail restart

2、sina.com的搭建

[root@mail ~]# service sendmail status sendmail (pid 2876) is running... [root@mail ~]# service sendmail restart

[root@mail ~]# netstat -tupln |grep dov

tcp 0 0 :::993 :::* LISTEN 2812/dovecot tcp 0 0 :::995 :::* LISTEN 2812/dovecot tcp 0 0 :::110 :::* LISTEN 2812/dovecot tcp 0 0 :::143 :::* LISTEN 2812/dovecot

[root@mail ~]# userdel -r user1

[root@mail ~]# userdel -r user2 [root@mail ~]# userdel -r user3

[root@mail ~]# useradd user5 [root@mail ~]# useradd user6 [root@mail ~]# passwd user5 Changing password for user user5. New UNIX password: BAD PASSWORD: it is WAY too short Retype new UNIX password: passwd: all authentication tokens updated successfully. [root@mail ~]# passwd user6 Changing password for user user6. New UNIX password: BAD PASSWORD: it is WAY too short Retype new UNIX password: passwd: all authentication tokens updated successfully.

[root@mail ~]# vim /etc/resolv.conf

[root@mail ~]# service sendmail restart

[root@mail ~]# service named start //dns一定要启动，否侧用户无法接收信件 Starting named: [ OK ]

[root@mail ~]# su - user5 [user5@mail ~]$ mail user6

[user5@mail ~]$ su - user6 Password: [user6@mail ~]$ mail

3、163.com与sina.com间的通信

[root@mail ~]# dig -t mx 163.com

[root@mail ~]# dig -t mx sina.com

4、在163.com上转发sina.com

[root@mail ~]# vim /var/named/chroot/etc/named.conf

[root@mail ~]# rndc reload server reload successful

[root@mail ~]# dig -t mx sina.com

5、在sina.com上转发163.com

[root@mail ~]# vim /var/named/chroot/etc/named.conf

[root@mail ~]# rndc reload

server reload successful

[root@mail ~]# dig -t mx 163.com

6、反向dns，减少延迟

163.com

[root@mail ~]# cd /var/named/chroot/etc/ You have new mail in /var/spool/mail/root [root@mail etc]# ll

[root@mail etc]# vim named.rfc1912.zones

[root@mail etc]# cd ../var/named/ [root@mail named]# pwd /var/named/chroot/var/named [root@mail named]# ll

[root@mail named]# cp -p named.local 192.168.101.zone [root@mail named]# ll

[root@mail named]# vim 192.168.101.zone

sina.com

[root@mail ~]# cd /var/named/chroot/etc/ [root@mail etc]# ll

[root@mail etc]# vim named.rfc1912.zones

[root@mail etc]# cd ../var/named/ [root@mail named]# pwd /var/named/chroot/var/named [root@mail named]# ll

[root@mail named]# cp -p named.local 192.168.101.zone

[root@mail named]# vim 192.168.101.zone

[root@mail named]# rndc reload server reload successful

7、地址解析

163.com

[root@mail named]# nslookup mail.sina.com

[root@mail named]# nslookup 192.168.101.6

sina.com

[root@mail named]# nslookup mail.163.com

[root@mail named]# nslookup 192.168.101.5

四、安全问题

1、邮件的机密性

[root@mail ~]# mount /dev/cdrom /mnt/cdrom/ mount: block device /dev/cdrom is write-protected, mounting read-only [root@mail ~]# cd /mnt/cdrom/Server/

[root@mail Server]# ll |grep shark -r--r--r-- 220 root root 11130359 Jun 11 2009 wireshark-1.0.8-1.el5_3.1.i386.rpm -r--r--r-- 220 root root 686650 Jun 11 2009 wireshark-gnome-1.0.8-1.el5_3.1.i386.rpm

[root@mail Server]# rpm -ivh wireshark-1.0.8-1.el5_3.1.i386.rpm error: Failed dependencies: libsmi.so.2 is needed by wireshark-1.0.8-1.el5_3.1.i386 [root@mail Server]# ll |grep smi -r--r--r-- 327 root root 2540456 Jan 18 2008 libsmi-0.4.5-2.el5.i386.rpm -r--r--r-- 327 root root 21212 Jan 18 2008 libsmi-devel-0.4.5-2.el5.i386.rpm -r--r--r-- 264 root root 62425 Apr 20 2009 psmisc-22.2-7.i386.rpm [root@mail Server]# rpm -ivh libsmi-0.4.5-2.el5.i386.rpm Preparing... ########################################### [100%] 1:libsmi ########################################### [100%] [root@mail Server]# rpm -ivh wireshark-1.0.8-1.el5_3.1.i386.rpm Preparing... ########################################### [100%] 1:wireshark ########################################### [100%]

[root@mail Server]# tshark -ni eth0 -R "tcp.dstport eq 110" //抓包

[root@mail Server]# vim /etc/pki/tls/openssl-f

[root@mail CA]# mkdir crl certs newcerts //产生此三个文件目录

[root@mail CA]# touch index.txt serial [root@mail CA]# echo "01" >serial [root@mail CA]# ll

[root@mail CA]# openssl genrsa 1024 >private/cakey.pem

[root@mail CA]# chmod 600 private/* //修改文件权限

[root@mail CA]# ll private/

[root@mail CA]# openssl req -new -key private/cakey.pem -x509 -days 3650 -out cacert.pem //产生证书

[root@mail CA]# ll

（1）、发送邮件加密

[root@mail CA]# mkdir -pv /etc/mail/certs mkdir: created directory `/etc/mail/certs' [root@mail CA]# cd /etc/mail/certs/ [root@mail certs]# pwd /etc/mail/certs [root@mail certs]# openssl genrsa 1024 >sendmail.key

[root@mail certs]# ll

[root@mail certs]# openssl req -new -key sendmail.key -out sendmail.csr

[root@mail certs]# ll

[root@mail certs]# openssl ca -in sendmail.csr -out sendmail.cert

[root@mail certs]# chmod 600 * [root@mail certs]# ll

[root@mail certs]# service sendmail restart

[root@mail certs]# telnet 127.0.0.1 25

[root@mail certs]# vim /etc/mail/sendmail.mc

[root@mail Server]# tshark -ni eth0 -R "tcp.dstport eq 25" //抓包

（2）、接收邮件加密

[root@mail ~]# mkdir -pv /etc/dovecot/certs mkdir: created directory `/etc/dovecot' mkdir: created directory `/etc/dovecot/certs' [root@mail ~]# cd /etc/dovecot/certs/

[root@mail certs]# openssl genrsa 1024 >dovecot.key

[root@mail certs]# openssl req -new -key dovecot.key -out dovecot.csr

[root@mail certs]# ll

[root@mail certs]# openssl ca -in dovecot.csr -out dovecot.cert

[root@mail certs]# vim /etc/dovecot.conf

[root@mail certs]# service dovecot restart

[root@mail certs]# netstat -tupln |grep dov tcp 0 0 :::993 :::* LISTEN 3993/dovecot tcp 0 0 :::995 :::* LISTEN 3993/dovecot tcp 0 0 :::110 :::* LISTEN 3993/dovecot tcp 0 0 :::143 :::* LISTEN 3993/dovecot

[root@mail certs]# vim /etc/dovecot.conf

[root@mail certs]# service dovecot restart

[root@mail certs]# netstat -tupln |grep dov tcp 0 0 :::995 :::* LISTEN 4026/dovecot

[root@mail certs]# tshark -ni eth0 -R "tcp.dstport eq 995 or tcp.srcport eq 995"

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