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根据SMTP协议流程Postfix可在以下规则内对客户端信息进行限制：

#https://www.haiyun.me
smtpd_client_restrictions = 
#客户端连接后匹配登录IP、反向查询在此匹配
smtpd_helo_restrictions = 
#客户端连接后以HELO显示送信方主机名称在此限制。
smtpd_sender_restrictions = 
#寄件人名称限制
smtpd_recipient_restrictions = 
#收件人名称限制
smtpd_data_restrictions = 
#内容限制，分header_check和check_body

Postfix过滤限制规则：
1.客户端SMTP连接时过滤：

smtpd_client_restrictions = 
     check_client_access = type:map #检查匹配表操作
     reject_rbl_client = #针对IP黑名单
     reject_rhsbl_client = #针对IP黑名单
     reject_unknown_client #拒绝客户地址没有反解及对应A记录

2.HELO阶段过滤：

smtpd_helo_restrictions = 
     check_helo_access = type:map #检查匹配表操作
     permit_naked_ip_address #允许直接使用ip地址的连接
     reject_invalid_hostname #拒绝无效格式的主机名
     reject_unknown_hostname  #拒绝未知的主机名连接，即无有效A或MX记录
     reject_no_fqdn_hostname #拒绝主机名非FQDN格式

3.发件人过滤，可在此限制Postfix发件人欺骗。

smtpd_sender_restrictions = 
     check_sender_access = type:map #检查匹配表操作
     reject_no_fqdn_sender #拒绝发件人非FQDN格式
     reject_rhsbl_sender = #发件人黑名单
     reject_unknown_sender_domain  #拒绝未知的发件人域，即无有效A或MX记录
     reject_sender_login_mismatch #拒绝登录用户与发件人不匹配

4.收件人过滤：

smtpd_recipient_restrictions = 
     check_recipient_access = type:map #检查匹配表操作
     permit_mynetworks      #mynetworks用户通过，匹配结束
     permit_sasl_authenticated  #sasl验证用户通过，匹配结束
     reject_unauth_destination #拒绝收件人非mydestination、relay_domains或virtual_alias_maps定义域邮件
     reject_no_fqdn_recipient  #拒绝收件人非FQDN格式
     reject_rhsbl_recipient = #收件人黑名单
     reject_unknown_recipient_domain  #拒绝未知的收件人域，即无有效A或MX记录

5.邮件内容过滤：

header_checks = pcre:/etc/postfix/header_checks
mime_header_checks = pcre:/etc/postfix/mime_header_checks
nested_header_checks = pcre:/etc/postfix/nested_header_checks
body_checks = pcre:/etc/postfix/body_checks

Postfix内网用户在转发邮件时可以任意填写发件人邮箱，给管理带来诸多不便，可以使用账号登录匹配发件人邮箱进行限制。
编辑Postfix配置文件：

#https://www.haiyun.me
cat /etc/postfix/main.cf
smtpd_sender_login_maps = hash:/etc/postfix/sasl_sender #用户与邮件账号匹配表
smtpd_sender_restrictions = 
      reject_sender_login_mismatch #拒绝发送邮件与登录用户不匹配的邮件
smtpd_recipient_restrictions =
#     permit_mynetworks,  #去除网络区域认证
      permit_sasl_authenticated #用户认证模式

新建用户与账号匹配表：

cat /etc/postfix/sasl_sender
root@www.haiyun.me       root

生成hash数据库：

postmap /etc/postfix/sasl_sender

伪造发件人发送邮件测试：

sendEmail -v -f test@www.haiyun.me -t mail@www.haiyun.me -s smtp.www.haiyun.me -u "test" -m "测试sendemail" -xu root -xp passwd
Feb 29 11:08:00 centos5 sendEmail[21973]: DEBUG => Connecting to smtp.www.haiyun.me:25
Feb 29 11:08:01 centos5 sendEmail[21973]: DEBUG => My IP address is: 192.168.1.3
Feb 29 11:08:01 centos5 sendEmail[21973]: SUCCESS => Received:     220 mail.www.haiyun.me ESMTP "ONOVPS Mail Server"
Feb 29 11:08:01 centos5 sendEmail[21973]: INFO => Sending:     EHLO centos5.7-x86
Feb 29 11:08:01 centos5 sendEmail[21973]: DEBUG => SMTP-AUTH: Using LOGIN authentication method
Feb 29 11:08:01 centos5 sendEmail[21973]: INFO => Sending:     AUTH LOGIN
Feb 29 11:08:01 centos5 sendEmail[21973]: SUCCESS => Received:     235 2.0.0 Authentication successful
Feb 29 11:08:01 centos5 sendEmail[21973]: DEBUG => User authentication was successful (Method: LOGIN)
Feb 29 11:08:01 centos5 sendEmail[21973]: INFO => Sending:     MAIL FROM:<test@www.haiyun.me>
Feb 29 11:08:01 centos5 sendEmail[21973]: SUCCESS => Received:     250 2.1.0 Ok
Feb 29 11:08:01 centos5 sendEmail[21973]: INFO => Sending:     RCPT TO:<mail@www.haiyun.me>
Feb 29 11:08:01 centos5 sendEmail[21973]: WARNING => The recipient <mail@www.haiyun.me> was rejected by the mail server, error follows:
Feb 29 11:08:01 centos5 sendEmail[21973]: WARNING => Received:     553 5.7.1 <test@www.haiyun.me>: Sender address rejected: not owned by user root
Feb 29 11:08:01 centos5 sendEmail[21973]: ERROR => Exiting. No recipients were accepted for delivery by the mail server.

生成用户、密码文件：

htpasswd -c /etc/httpd/passwd user

1.直接编辑Apache配置添加认证：

#https://www.haiyun.me
<Directory "/var/www/html">
Options Indexes FollowSymLinks
AllowOverride None
Order allow,deny
Allow from all
AuthName "Httpd Access"
AuthType Basic
AuthUserFile /etc/httpd/passwd
Require valid-user
</Directory>

2.以.htaccess认证，首先授权相应网站建.htaccess验证权限：

Options Indexes FollowSymLinks
AllowOverride AuthConfig 
Order allow,deny
Allow from all

在验证目录新建.htaccess文件：

AuthName "Httpd Access"
AuthType Basic
AuthUserFile /etc/httpd/passwd
Require valid-user

首先生成SSL证书，如需SSL证书认证可先生成证书请求文件再转交CA认证。
Postfix配置SSL：

#https://www.haiyun.me
cat /etc/postfix/main.cf
#smtpd_tls_auth_only = yes
smtpd_tls_key_file = /etc/postfix/CA/private/server.key
smtpd_tls_cert_file = /etc/postfix/CA/certs/server.crt
smtpd_tls_CAfile = /etc/postfix/CA/cacert.pem
smtpd_tls_loglevel = 1
smtpd_tls_received_header = yes
smtpd_tls_session_cache_timeout = 3600s
tls_random_source = dev:/dev/urandom

开启Postfix服务器SMTPS端口监听：

cat /etc/postfix/master.cf
smtps     inet  n       -       n       -       -       smtpd
  -o smtpd_tls_wrappermode=yes
  -o smtpd_sasl_auth_enable=yes
  -o smtpd_client_restrictions=permit_sasl_authenticated,reject

测试SMTP SSL是否生效：

openssl s_client -connect smtp.haiyun.me:smtps
SSL-Session:
    Protocol  : TLSv1
    Cipher    : DHE-RSA-AES256-SHA
    Session-ID: 65424E5937C2EE0453E796BA179DF8F8D92A523FAD5F170CFE11A64E5A0441D3
    Session-ID-ctx: 
    Master-Key: 43EC9C65F8215B3304C62A4E860116D6CA58BFE732514F5B31EC67196D993F43A19E837CA9BD48D6008A06874ED83BB0
    Key-Arg   : None
    Krb5 Principal: None
    Start Time: 1341366288
    Timeout   : 300 (sec)
    Verify return code: 19 (self signed certificate in certificate chain)
---
220 mail.www.haiyun.me ESMTP Postfix
quit
221 2.0.0 Bye

Dovecot配置SSL：

cat /etc/dovecot/conf.d/10-ssl.conf
ssl = yes
ssl_cert = </etc/pki/dovecot/certs/dovecot.pem
ssl_key = </etc/pki/dovecot/private/dovecot.pem

测试IMAP/POP SSL是否生效：

openssl s_client -connect smtp..haiyun.me:imaps
openssl s_client -connect smtp..haiyun.me:pops
SSL-Session:
    Protocol  : TLSv1
    Cipher    : DHE-RSA-AES256-SHA
    Session-ID: A6CD69E16438BB8CBEA7ABCDF74F1BDC844E00C4C7A3B2446FB87E230788D4A5
    Session-ID-ctx: 
    Master-Key: D6135140AC6BAD1AABFD85CE1A28FA66387B60CF6E6744B0F3BDCEFB82F6B7EA4FF28461E6A007DC03B91787C50CDFE0
    Key-Arg   : None
    Krb5 Principal: None
    Start Time: 1341363344
    Timeout   : 300 (sec)
    Verify return code: 18 (self signed certificate)
---
* OK Dovecot ready.

1.修改Openssl配置文件CA目录：

cat /etc/pki/tls/openssl.cnf
dir             = /etc/pki/CA

2.生成根证书及私钥：

#https://www.haiyun.me
cd /etc/pki/CA
mkdir private crl certs newcerts #新建证书存放目录
echo '00' > serial #新建serial文件并写入初始序列号00
touch index.txt #新建index.txt空文件
openssl genrsa -out private/cakey.pem 1024 #生成CA根证书私钥
openssl req -new -x509 -key private/cakey.pem  -out cacert.pem #生成CA根证书

3.生成服务器证书私钥、证书，可用于https服务器等。

openssl genrsa -out private/server.key 1024
openssl req -new -key private/server.key -out crl/server.csr #生成证书请求文件，可提供认证CA签核，或自签名。
openssl ca -in crl/server.csr -out certs/server.crt #自签名证书