邮件系统的安全性通过两个方面：

第一方面：发送与接收（通过协议进行加密）

发送加密（点对点）：

通过协议smtp与ssl的结合——》smtps

smtps：

1：使用965端口（smtps）

2：利用25端口直接进行加密：stmp+ssl（即starttls）

查看编译时是否支持starttls

查看在编译时是否加密：

3：（端对端）在ftp上与第三方工具（gpg）进行加密。（即s/mime）

接收加密：

通过协议pop2/3与ssl的结合——》pops

通过协议imap与ssl的结合——》imaps

第二方面：身份验证

启动STARTTLS进行加密：

编译制作颁发机构

[root@mail  ~]# cd /etc/pki/
[root@mail pki]# ll
total 36
drwx------ 3 root root 4096 Feb  9 00:16 CA
drwxr-xr-x 4 root root 4096 Mar 20 10:27 dovecot
drwxr-xr-x 2 root root 4096 Feb  9 00:15 nssdb
drwxr-xr-x 2 root root 4096 Feb  9 00:15 rpm-gpg
drwxr-xr-x 5 root root 4096 Mar 20 19:37 tls
[root@mail pki]# vim tls/openssl.cnf

[root@mail pki]# cd CA   切换到CA目录
[root@mail CA]# mkdir certs crl newcerts     创建3个目录
[root@mailt CA]# touch index.txt serial    创建2个文档
[root@mail CA]# echo "01" >serial    赋予serial序列号
[root@mail CA]# ll       查看
total 24
drwxr-xr-x 2 root root 4096 Mar 20 20:08 certs
drwxr-xr-x 2 root root 4096 Mar 20 20:08 crl
-rw-r--r-- 1 root root    0 Mar 20 20:08 index.txt
drwxr-xr-x 2 root root 4096 Mar 20 20:08 newcerts
drwx------ 2 root root 4096 Jun 30  2009 private
-rw-r--r-- 1 root root    3 Mar 20 20:09 serial
创建私钥：

[root@mail CA]# openssl genrsa 1024 >private/cakey.pem
Generating RSA private key, 1024 bit long modulus
..........++++++
.++++++
e is 65537 (0x10001)
创建营业执照：

[root@mail CA]# openssl req -new -x509 -key private/cakey.pem -out cacert.pem -days 3650
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) [GB]:CN
State or Province Name (full name) [Berkshire]:BEIJING
Locality Name (eg, city) [Newbury]:BEIJING
Organization Name (eg, company) [My Company Ltd]:SECCENTER     
Organizational Unit Name (eg, section) []:tec
Common Name (eg, your name or your server's hostname) []:rootca.net.net
Email Address []:
[root@localhost CA]# ll
total 28
-rw-r--r-- 1 root root 1155 Mar 20 20:17 cacert.pem
drwxr-xr-x 2 root root 4096 Mar 20 20:08 certs
drwxr-xr-x 2 root root 4096 Mar 20 20:08 crl
-rw-r--r-- 1 root root    0 Mar 20 20:08 index.txt
drwxr-xr-x 2 root root 4096 Mar 20 20:08 newcerts
drwx------ 2 root root 4096 Mar 20 20:11 private
-rw-r--r-- 1 root root    3 Mar 20 20:09 serial
[root@mail CA]# chmod 600 private/*       更改钥匙权限
[root@mail CA]# mkdir /etc/mail/certs      创建目录
[root@mail CA]# cd /etc/mail/certs/     切换到目录
[root@mail certs]# ll     查看
total 0
产生钥匙：

[root@mail certs]# openssl genrsa 1024 >sendmail.key      
Generating RSA private key, 1024 bit long modulus
...........++++++
.++++++
e is 65537 (0x10001)
根据钥匙做请求文件：

[root@mail certs]# openssl req -new  -key sendmail.key -out sendmail.csr          
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) [GB]:CN    
State or Province Name (full name) [Berkshire]:HENAN
Locality Name (eg, city) [Newbury]:ZHENGZHOU
Organization Name (eg, company) [My Company Ltd]:zzdx
Organizational Unit Name (eg, section) []:tec
Common Name (eg, your name or your server's hostname) []:mail.bj.com
Email Address []:

Please enter the following 'extra' attributes
to be sent with your certificate request
A challenge password []:
An optional company name []:
根据钥匙请求文件得到证书：

[root@mail certs]# openssl ca -in sendmail.csr -out sendmail.cert
Using configuration from /etc/pki/tls/openssl.cnf
Check that the request matches the signature
Signature ok
Certificate Details:
        Serial Number: 1 (0x1)
        Validity
            Not Before: Mar 20 12:27:04 2012 GMT
            Not After : Mar 20 12:27:04 2013 GMT
        Subject:
           countryName               = CN
            stateOrProvinceName       = HENAN
            organizationName          = zzdx
            organizationalUnitName    = tec
            commonName                = mail.bj.com
        X509v3 extensions:
            X509v3 Basic Constraints:
                CA:FALSE
            Netscape Comment:
                OpenSSL Generated Certificate
            X509v3 Subject Key Identifier:
                54:FA:EA:A7:E0:8B:72:DF:57:37:4E:41:84:AA:BA:1A:AB:C4:B7:C9
            X509v3 Authority Key Identifier:
                keyid:8F:9B:34:8D:DA:DD:63:D5:0B:07:AF:F4:E4:E0:C9:6C:04:44:65:CC

Certificate is to be certified until Mar 20 12:27:04 2013 GMT (365 days)
Sign the certificate? [y/n]:y

1 out of 1 certificate requests certified, commit? [y/n]y
Write out database with 1 new entries
Data Base Updated

[root@mail certs]# ll     查看证书
total 12
-rw-r--r-- 1 root root 3075 Mar 20 20:27 sendmail.cert
-rw-r--r-- 1 root root  647 Mar 20 20:23 sendmail.csr
-rw-r--r-- 1 root root  887 Mar 20 20:19 sendmail.key

[root@mail certs]#cp /etc/pki/CA/cacert.pem  .    把证书拷贝当前目录下

[root@mail certs]# ll     查看
total 16
-rw-r--r-- 1 root root 1155 Mar 12 12:07 cacert.pem
-rw-r--r-- 1 root root 3074 Mar 12 12:06 sendmail.cert
-rw-r--r-- 1 root root  647 Mar 12 12:05 sendmail.csr
-rw-r--r-- 1 root root  887 Mar 12 12:02 sendmail.key
[root@mail certs]# cd ..
[root@mail mail]# vim sendmail.mc    编辑sendmail配置脚本

 
[root@mail mail]# service sendmail restart     重新启动sendmail
Shutting down sm-client:                                   [  OK  ]
Shutting down sendmail:                                    [  OK  ]
Starting sendmail:                                         [  OK  ]
Starting sm-client:                                        [  OK  ]

查看日志：tail –f /var/log/maillog

[root@mail mail]# cd certs/
[root@mail certs]# ll
total 16
-rw-r--r-- 1 root root 1155 Mar 12 12:07 cacert.pem
-rw-r--r-- 1 root root 3074 Mar 12 12:06 sendmail.cert
-rw-r--r-- 1 root root  647 Mar 12 12:05 sendmail.csr
-rw-r--r-- 1 root root  887 Mar 12 12:02 sendmail.key
[root@mail certs]# chmod 600 *       更改权限
[root@mail certs]# ll
total 16
-rw------- 1 root root 1155 Mar 12 12:07 cacert.pem
-rw------- 1 root root 3074 Mar 12 12:06 sendmail.cert
-rw------- 1 root root  647 Mar 12 12:05 sendmail.csr
-rw------- 1 root root  887 Mar 12 12:02 sendmail.key
[root@mail certs]# service sendmail restart
Shutting down sm-client:                                   [  OK  ]
Shutting down sendmail:                                    [  OK  ]
Starting sendmail:                                         [  OK  ]
Starting sm-client:                                        [  OK  ]

用Outlook  Express查看是否加密：

创建用户user1

 

更改user1的属性：

设置dns指向

发送一封邮件给自己：

查看日志：(starttls 启动)

安装抓包工具截取明文邮件的账号：

[root@mail ~]# cd /mnt/cdrom/Server/
[root@mail Server]#vim /etc/yum.repos.d/rhel-debuginfo.repo

[root@mail Server]# yum list all |grep wir      搜索含wir的包
Repository rhel-server is listed more than once in the configuration
This system is not registered with RHN.
RHN support will be disabled.
wireless-tools.i386                    1:28-2.el5            installed         
wireshark.i386                         1.0.8-1.el5_3.1       rhel-server         
wireless-tools-devel.i386              1:28-2.el5            rhel-server       
wireshark-gnome.i386                   1.0.8-1.el5_3.1       rhel-server       
[root@mail Server]# yum install wireshark        安装wireshark

启用抓包工具：（当用户接收邮件时：会显示用户名和密码）

为了安全为了用户所以接收时也要进行加密：

[root@mail certs]# mkdir -pv /etc/dovecot/certs     创建目录

mkdir：created directory `/etc/dovecot`

mkdir: created directory `/etc/dovecot/certs`

[root@mail certs]# cd /etc/dovecot/certs/      切换到certs目录

做钥匙：

[root@mail certs]# openssl genrsa 1024 >dovecot.key
Generating RSA private key, 1024 bit long modulus
...........++++++
.++++++
e is 65537 (0x10001)
产生请求文件：

[root@mail certs]# openssl req -new -key dovecot.key -out dovecot.csr
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) [GB]:CN
State or Province Name (full name) [Berkshire]:HENAN
Locality Name (eg, city) [Newbury]:ZHENGZHOU
Organization Name (eg, company) [My Company Ltd]:zzdx
Organizational Unit Name (eg, section) []:tec
Common Name (eg, your name or your server's hostname) []:pop3.bj.com
Email Address []:

Please enter the following 'extra' attributes
to be sent with your certificate request
A challenge password []:
An optional company name []:

获得证书：

[root@mail certs]# openssl ca -in dovecot.csr -out dovecot.cert
Using configuration from /etc/pki/tls/openssl.cnf
Check that the request matches the signature
Signature ok
Certificate Details:
         Serial Number: 2 (0x2)
Validity
       Not Before: Mar 20 12:27:04 2012 GMT
       Not After : Mar 20 12:27:04 2013 GMT
Subject:
                           countryName = CN
                          stateOrProvinceName = HENAN
                          organizationName = zzdx
                          organizationalUnitName = tec
                          commonName = pop3.bj.com
    X509v3 extensions:
                X509v3 Basic Constraints:
                        CA:FALSE
                Netscape Comment:
                        OpenSSL Generated Certificate
                X509v3 Subject Key Identifier: 
                 54:FA:EA:A7:E0:8B:72:DF:57:37:4E:41:84:AA:BA:1A:AB:C4:B7:C9
                X509v3 Authority Key Identifier:
      keyid:8F:9B:34:8D:DA:DD:63:D5:0B:07:AF:F4:E4:E0:C9:6C:04:44:65:CC

Certificate is to be certified until Mar 20 12:27:04 2013 GMT (365 days)
Sign the certificate? [y/n]:y

1 out of 1 certificate requests certified, commit? [y/n]y
Write out database with 1 new entries
Data Base Updated

[root@mail certs]# ll       查看证书
total 16
-rw-r--r-- 1 root root 3074 Mar 12 12:06 dovecot.cert
-rw-r--r-- 1 root root  647 Mar 12 12:05 dovecot.csr
-rw-r--r-- 1 root root  887 Mar 12 12:02 dovecot.key
[root@mail certs]# chmod 600 *      更改权限
[root@mail certs]# ll
total 16
--rw------- 1 root root 3074 Mar 12 12:06 dovecot.cert
-rw------- 1 root root  647 Mar 12 12:05 dovecot.csr
-rw------- 1 root root  887 Mar 12 12:02 dovecot.key

[root@mail certs]# vim /etc/dovecot.conf      更改配置脚本

 
[root@mail certs]# service dovecot restart       重新启动dovecot
Stopping Dovecot Imap:                                     [  OK  ]
Starting Dovecot Imap:                                     [  OK  ]
[root@mail certs]# netstat -tupln |grep dov         查看端口
tcp        0      0 :::993                      :::*                        LISTEN      4757/dovecot       
tcp        0      0 :::110                      :::*                        LISTEN      4757/dovecot       
tcp        0      0 :::143                      :::*                        LISTEN      4757/dovecot       
用客户进行测试（加密的端口）：

必须新建一个用户：

更改用户user1的属性：

然后让用户user1接收邮件查看日志：

认证sasl（简单认证安全协议）   服务器是saslauthd

查看与有关的包：

[root@mail Server]# cd
[root@mail ~]# rpm -qa |grep sasl
cyrus-sasl-lib-2.1.22-5.el5      连接库包
cyrus-sasl-2.1.22-5.el5（很重要的包） 
cyrus-sasl-devel-2.1.22-5.el5       开发包
cyrus-sasl-plain-2.1.22-5.el5        验证方法包
[root@mail ~]# cd /mnt/cdrom/Server/       切换到光盘上
[root@mail Server]# ll |grep sasl      查找关于sasl的包
-r--r--r-- 103 root root  1251623 Jul 29  2009 cyrus-sasl-2.1.22-5.el5.i386.rpm
-r--r--r--  99 root root  1418364 Jul 29  2009 cyrus-sasl-devel-2.1.22-5.el5.i386.rpm
-r--r--r-- 103 root root    28967 Jul 29  2009 cyrus-sasl-gssapi-2.1.22-5.el5.i386.rpm
-r--r--r-- 103 root root    24390 Jul 29  2009 cyrus-sasl-ldap-2.1.22-5.el5.i386.rpm
-r--r--r-- 103 root root   129180 Jul 29  2009 cyrus-sasl-lib-2.1.22-5.el5.i386.rpm
-r--r--r-- 103 root root    46415 Jul 29  2009 cyrus-sasl-md5-2.1.22-5.el5.i386.rpm
-r--r--r-- 103 root root    32054 Jul 29  2009 cyrus-sasl-ntlm-2.1.22-5.el5.i386.rpm
-r--r--r-- 103 root root    27027 Jul 29  2009 cyrus-sasl-plain-2.1.22-5.el5.i386.rpm
-r--r--r-- 103 root root    27330 Jul 29  2009 cyrus-sasl-sql-2.1.22-5.el5.i386.rpm
-r--r--r-- 278 root root    39119 Jan 19  2007 gnu-crypto-sasl-jdk1.4-2.1.0-2jpp.1.i386.rpm
[root@mail Server]# chkconfig --list |grep sasl     查看验证服务器情况
saslauthd          0:off    1:off    2:off    3:off    4:off    5:off    6:off
[root@mail Server]# service saslauthd start       启动saslauthd
Starting saslauthd:                                        [  OK  ]
[root@mail Server]# chkconfig saslauthd on       设置成开机启动
[root@mail Server]# vim /usr/lib/sasl2/Sendmail.conf      编辑服务器配置脚本

[root@mail Server]# vim /etc/mail/sendmail.mc    改写sendmail配置脚本

[root@mail Server]# service sendmail restart      重新启动sendmail
Shutting down sm-client:                                   [  OK  ]
Shutting down sendmail:                                    [  OK  ]
Starting sendmail:                                         [  OK  ]
Starting sm-client:                                        [  OK  ]
进行测试身份验证：

[root@mail Server]# telnet 127.0.0.1 25
Trying 127.0.0.1...
Connected to mail.bj.com (127.0.0.1).
Escape character is '^]'.
220 mail.bj.com ESMTP Sendmail 8.13.8/8.13.8; Mon, 12 Mar 2012 17:48:52 +0800
EHLO 127.0.0.1   
250-mail.bj.com Hello mail.bj.com [127.0.0.1], pleased to meet you
250-ENHANCEDSTATUSCODES
250-PIPELINING
250-8BITMIME
250-SIZE
250-DSN
250-ETRN
250-AUTH LOGIN PLAIN
250-STARTTLS
250-DELIVERBY
250 HELP
MAIL FROM:USER10@BJ.COM                       虽然需要验证但是还可以匿名
250 2.1.0 USER10@BJ.COM... Sender ok       发送邮件说明这不是强制的验证
quit     
221 2.0.0 mail.bj.com closing connection
Connection closed by foreign host.

编辑sendmail配置脚本使发邮件的用户需要强制的进行验证：
[root@mail Server]# vim /etc/mail/sendmail.mc

[root@mail Server]# service sendmail restart      重新启动sendmail
Shutting down sm-client:                                   [  OK  ]
Shutting down sendmail:                                    [  OK  ]
Starting sendmail:                                         [  OK  ]
Starting sm-client:                                        [  OK  ]
再次的进行身份验证测试：发送邮件

[root@mail Server]# telnet 127.0.0.1 25
Trying 127.0.0.1...
Connected to mail.bj.com (127.0.0.1).
Escape character is '^]'.
220 mail.bj.com ESMTP Sendmail 8.13.8/8.13.8; Mon, 12 Mar 2012 18:29:08 +0800
EHLO 127.0.0.1
250-mail.bj.com Hello mail.bj.com [127.0.0.1], pleased to meet you
250-ENHANCEDSTATUSCODES
250-PIPELINING
250-8BITMIME
250-SIZE
250-DSN
250-AUTH LOGIN PLAIN
250-STARTTLS
250-DELIVERBY
250 HELP
MAIL FROM:user10@bj.com
530 5.7.0 Authentication required  需要验证不是合法的用户无法发送邮件
AUTH LOGIN cm9vdA==        输入有效的用户的类似base64编码

334 UGFzc3dvcmQ6
MTIzNDU2
235 2.0.0 OK Authenticated
MAIL FROM:root@bj.com          验证完之后要再次的输入root邮箱
250 2.1.0 root@bj.com... Sender ok
RCPT TO:user1@bj.com
250 2.1.5 user1@bj.com... Recipient ok
DATA
354 Enter mail, end with "." on a line by itself
4444444444444           邮件内容
.           结束
250 2.0.0 q2CAT8jA005317 Message accepted for delivery
quit          退出
221 2.0.0 mail.bj.com closing connection
Connection closed by foreign host.

用user1登陆查看邮件：

[root@mail Server]# su – user1

[user1@mail ~]$ mail

Mail version 8.1 6/6/93.  Type ? for help.
"/var/spool/mail/user1": 2 messages 1 new
    1 MAILER-DAEMON@mail.b  Sun Mar 11 23:30  13/542   "DON'T DELETE THIS MESSAGE -- FOLDER INTE"
>N  2 root@bj.com           Mon Mar 12 18:41  12/390 
& 2              查看邮件2
Message 2:
From root@bj.com  Mon Mar 12 18:41:28 2012
Date: Mon, 12 Mar 2012 18:29:08 +0800
From: root <root@bj.com>

4444444444444

& exit         退出

在windows上用用户user1给自己发送邮件：

发送过程中会出现：出错信息

查看日志：看到

要想发送成功必须设置user1的属性服务器中的登陆于接收邮件具有相同的配置：然后发送

编写邮件发给root：

查看日志：