三、为postfix开启基于cyrus-sasl的认证功能
使用以下命令验正postfix是否支持cyrus风格的sasl认证，如果您的输出为以下结果，则是支持的：
# postconf -a
cyrus
dovecot
#vi /etc/postfix/main.cf
添加以下内容：
############################CYRUS-SASL############################
broken_sasl_auth_clients = yes
smtpd_recipient_restrictions=permit_mynetworks,permit_sasl_authenticated,reject_invalid_hostname,reject_non_fqdn_hostname,reject_unknown_sender_domain,reject_non_fqdn_sender,reject_non_fqdn_recipient,reject_unknown_recipient_domain,reject_unauth_pipelining,reject_unauth_destination
smtpd_sasl_auth_enable = yes
smtpd_sasl_local_domain = $myhostname
smtpd_sasl_security_options = noanonymous
smtpd_sasl_application_name = smtpd
smtpd_banner = Welcome to our $myhostname ESMTP,Warning: Version not Available!
#vi /usr/local/lib/sasl2/smtpd.conf
添加如下内容：
pwcheck_method: saslauthd
mech_list: PLAIN LOGIN
让postfix重新加载配置文件
# postfix reload
# telnet mail.luowei.com 25
Trying 127.0.0.1...
Connected to localhost.localdomain (127.0.0.1).
Escape character is '^]'.
220 Welcome to our mail.luowei.com ESMTP,Warning: Version not Available!
ehlo mail.test.com
250-mail.test.com
250-PIPELINING
250-SIZE 10240000
250-VRFY
250-ETRN
250-AUTH PLAIN LOGIN
250-AUTH=PLAIN LOGIN （请确保您的输出以类似两行）
250-ENHANCEDSTATUSCODES
250-8BITMIME
250 DSN
四、安装Courier authentication library
# tar jxvf courier-authlib-0.62.4.tar.bz2 //使用新版本
# cd courier-authlib-0.62.4
#./configure \
--prefix=/usr/local/courier-authlib \
--sysconfdir=/etc \
--with-authmysql \
--with-mysql-libs=/usr/lib/mysql \
--with-mysql-includes=/usr/include/mysql \
--with-RedHat \
--with-authmysqlrc=/etc/authmysqlrc \
--with-authdaemonrc=/etc/authdaemonrc \
--with-ltdl-lib=/usr/lib \
--with-ltdl-include=/usr/include
# make
# make install
# chmod 755 /usr/local/courier-authlib/var/spool/authdaemon
# cp /etc/authdaemonrc.dist /etc/authdaemonrc
# cp /etc/authmysqlrc.dist /etc/authmysqlrc
修改/etc/authdaemonrc 文件
authmodulelist="authmysql"
authmodulelistorig="authmysql"
daemons=10
编辑/etc/authmysqlrc 为以下内容，其中2525，2525 为postfix 用户的UID和GID。
MYSQL_SERVER localhost
MYSQL_PORT 3306 (指定你的mysql监听的端口，这里使用默认的3306)
MYSQL_USERNAME extmail (这时为后文要用的数据库的所有者的用户名)
MYSQL_PASSWORD extmail (密码)
MYSQL_SOCKET /var/lib/mysql/mysql.sock
MYSQL_DATABASE extmail
MYSQL_USER_TABLE mailbox
MYSQL_CRYPT_PWFIELD password
MYSQL_UID_FIELD '2525'
MYSQL_GID_FIELD '2525'
MYSQL_LOGIN_FIELD username
MYSQL_HOME_FIELD concat('/var/mailbox/',homedir)
MYSQL_NAME_FIELD name
MYSQL_MAILDIR_FIELD concat('/var/mailbox/',maildir)
# cp courier-authlib.sysvinit /etc/init.d/courier-authlib
# chmod 755 /etc/init.d/courier-authlib
# chkconfig --add courier-authlib
# chkconfig --level 2345 courier-authlib on
#echo "/usr/local/courier-authlib/lib/courier-authlib" >> /etc/ld.so.conf.d/courier-authlib.conf
# ldconfig -v
# service courier-authlib start (启动服务)
新建虚拟用户邮箱所在的目录，并将其权限赋予postfix用户：
#mkdir –pv /var/mailbox
#chown –R postfix /var/mailbox
接下来重新配置SMTP 认证，编辑 /usr/local/lib/sasl2/smtpd.conf ，确保其为以下内容：
pwcheck_method: authdaemond
log_level: 3
mech_list:PLAIN LOGIN
authdaemond_path:/usr/local/courier-authlib/var/spool/authdaemon/socket
五、让postfix支持虚拟域和虚拟用户
1、编辑/etc/postfix/main.cf，添加如下内容：
########################Virtual Mailbox Settings########################
virtual_mailbox_base = /var/mailbox
virtual_mailbox_maps = mysql:/etc/postfix/mysql_virtual_mailbox_maps.cf
virtual_mailbox_domains = mysql:/etc/postfix/mysql_virtual_domains_maps.cf
virtual_alias_domains =
virtual_alias_maps = mysql:/etc/postfix/mysql_virtual_alias_maps.cf
virtual_uid_maps = static:2525
virtual_gid_maps = static:2525
virtual_transport = virtual
maildrop_destination_recipient_limit = 1
maildrop_destination_concurrency_limit = 1
##########################QUOTA Settings########################
message_size_limit = 14336000
virtual_mailbox_limit = 20971520
virtual_create_maildirsize = yes
virtual_mailbox_extended = yes
virtual_mailbox_limit_maps = mysql:/etc/postfix/mysql_virtual_mailbox_limit_maps.cf
virtual_mailbox_limit_override = yes
virtual_maildir_limit_message = Sorry, the user's maildir has overdrawn his diskspace quota, please Tidy your mailbox and try again later.
virtual_overquota_bounce = yes
2、使用extman源码目录下docs目录中的extmail.sql和init.sql建立数据库：
# tar zxvf extman-1.1.tar.gz
# cd extman-1.1/docs
# mysql -u root -p <extmail.sql
# mysql -u root -p <init.sql
# cp mysql* /etc/postfix/
3、授予用户extmail访问extmail数据库的权限
# mysql -uroot -p
输入密码就可以进入了，这个密码就是上面配置的密码
mysql> mysql -uroot -p //输入密码进入
mysql> GRANT ALL PRIVILEGES ON extmail.* TO extmail@localhost IDENTIFIED BY 'extmail';
mysql> GRANT ALL PRIVILEGES ON extmail.* TO extmail@127.0.0.1 IDENTIFIED BY 'extmail';
说明：启用虚拟域以后，需要取消中心域，即注释掉myhostname, mydestination, mydomain, myorigin几个指令；当然，你也可以把mydestionation的值改为你自己需要的。