qmail系统的邮箱一天起码要收十几份垃圾、病毒邮件，实在是比较烦，不是很喜欢qmail，特别是日志，让人不知所云，所以干脆考虑更换邮件系统。
系统平台为Debian Woody 3.0
一、邮件系统的安装
1、软件包安装
Postfix+Courier-IMAP+Cyrus-SASL+PAM_MySQL+MySQL这种安装方式简单易行，在Debian下的安装更加方便：
# apt-get install courier-pop postfix-mysql postfix-tls courier-authdaemoncourier-authmysql libpam-mysql libsasl7 libsasl-modules-plain courier-imap
如果你的系统本身没有mysql，那么在上面的列表里还要加上mysql-server。apt在安装过程中会有简单的提示，要求填上系统的域名等信息。
2、postfix的配置
修改main.cf：
添加：
home_mailbox = Maildir/
告诉postfix使用Maildir方式
mydestination = $myhostname, $transport_maps
告诉postfix发送$myhostname（本机）和$transport_maps（transport表里的域名）的邮件。
alias_maps = mysql:/etc/postfix/mysql-aliases.cf
relocated_maps = mysql:/etc/postfix/mysql-relocated.cf
transport_maps = mysql:/etc/postfix/mysql-transport.cf
virtual_maps = mysql:/etc/postfix/mysql-virtual.cf
告诉postfix从哪里找这些表。
local_recipient_maps = $alias_maps $virtual_mailbox_maps unix:passwd.byname
postfix传递给本地收件人的几种方法。
virtual_mailbox_base = /home/vmail
virtual_mailbox_maps = mysql:/etc/postfix/mysql-virtual-maps.cf
virtual_uid_maps = mysql:/etc/postfix/mysql-virtual-uid.cf
virtual_gid_maps = mysql:/etc/postfix/mysql-virtual-gid.cf
虚拟用户的信息。
broken_sasl_auth_clients = yes
smtpd_sasl_auth_enable = yes
smtpd_sasl_security_options = noanonymous
启用sasl，必须验证才能发信。
smtpd_recipient_restrictions = permit_mynetworks,permit_sasl_authenticated,reject_unknown_recipient_domain,reject_non_fqdn_recipient,check_relay_domains
发信限制。
还可以加上一些其他的参数：
disable_vrfy_command = yes
将vrfy功能关掉。
3、与MySQL结合的配置及数据表结构
注意：配置mysql相关部分要写127.0.0.1而不要写localhost，如果使用localhost，postfix会尝试socket连接。debian的postfix使用socket连接好像有问题。mysql不能使用skip-networking选项，要使用--bind-address=127.0.0.1让它监听在127.0.0.1。（非常感谢Martin List-Petersen指点）还有要注意的是如果是自己编译的mysql，建议在启动的时候加上--socket=/var/run/mysqld/mysqld.sock参数，因为pam-mysql又需要使用这个socket。如果你的apache+php是自己编译的话，php又需要重新编译，配置的时候需要加上--with-mysql-sock=/var/run/mysqld/mysqld.sock参数。是不是比较烦？这不过是个开始。
MySQL的数据表：
CREATE TABLE alias (
id int(11) unsigned NOT NULL auto_increment,
alias varchar(128) NOT NULL default '',
destination varchar(128) NOT NULL default '',
PRIMARY KEY (id)
) TYPE=MyISAM;
CREATE TABLE relocated (
id int(11) unsigned NOT NULL auto_increment,
email varchar(128) NOT NULL default '',
destination varchar(128) NOT NULL default '',
PRIMARY KEY (id)
) TYPE=MyISAM;
CREATE TABLE transport (
id int(11) unsigned NOT NULL auto_increment,
domain varchar(128) NOT NULL default '',
destination varchar(128) NOT NULL default '',
PRIMARY KEY (id),
UNIQUE KEY domain (domain)
) TYPE=MyISAM;
CREATE TABLE users (
id int(11) unsigned NOT NULL auto_increment,
email varchar(128) NOT NULL default '',
clear varchar(128) NOT NULL default '',
name tinytext NOT NULL,
uid int(11) unsigned NOT NULL default '1011',
gid int(11) unsigned NOT NULL default '1011',
homedir tinytext NOT NULL,
maildir tinytext NOT NULL,
quota tinytext NOT NULL,
postfix enum('Y','N') NOT NULL default 'Y',
PRIMARY KEY (id),
UNIQUE KEY email (email)
) TYPE=MyISAM;
CREATE TABLE virtual (
id int(11) unsigned NOT NULL auto_increment,
email varchar(128) NOT NULL default '',
destination varchar(128) NOT NULL default '',
PRIMARY KEY (id)
) TYPE=MyISAM;
/etc/postfix目录下各mysql配置文件：
mysql-aliases.cf
user = mysql-postfix-user
password = mysql-postfix-pass
dbname = postfix
table = alias
select_field = destination
where_field = alias
hosts = 127.0.0.1
mysql-relocated.cf
user = mysql-postfix-user
password = mysql-postfix-pass
dbname = postfix
table = relocated
select_field = destination
where_field = email
hosts = 127.0.0.1
mysql-transport.cf
user = mysql-postfix-user
password = mysql-postfix-pass
dbname = postfix
table = transport
select_field = destination
where_field = domain
hosts = 127.0.0.1
mysql-virtual.cf
user = mysql-postfix-user
password = mysql-postfix-pass
dbname = postfix
table = virtual
select_field = destination
where_field = email
hosts = 127.0.0.1
mysql-virtual-maps.cf
user = mysql-postfix-user
password = mysql-postfix-pass
dbname = postfix
table = users
select_field = maildir
where_field = email
additional_conditions = and postfix = 'y'
hosts = 127.0.0.1
mysql-virtual-uid.cf
user = mysql-postfix-user
password = mysql-postfix-pass
dbname = postfix
table = users
select_field = uid
where_field = email
additional_conditions = and postfix = 'y'
hosts = 127.0.0.1
mysql-virtual-gid.cf
user = mysql-postfix-user
password = mysql-postfix-pass
dbname = postfix
table = users
select_field = gid
where_field = email
additional_conditions = and postfix = 'y'
hosts = 127.0.0.1
修改Courier相关设置，/etc/courier/imapd:
AUTHMODULES="authdaemon"
IMAP_CAPABILITY="IMAP4rev1 CHILDREN NAMESPACE THREAD=ORDEREDSUBJECT THREAD=REFERENCES SORT AUTH=CRAM-MD5 AUTH=CRAM-SHA1 IDLE"
修改/etc/courier/pop3d
AUTHMODULES="authdaemon"
POP3AUTH="LOGIN CRAM-MD5 CRAM-SHA1"
修改/etc/courier/authdaemonrc
authmodulelist="authmysql authpam"
使用mysql验证和pam验证。
修改/etc/courier/authmysqlrc
MYSQL_SERVER 127.0.0.1
MYSQL_USERNAME mysql-postfix-user
MYSQL_PASSWORD mysql-postfix-pass
#MYSQL_SOCKET /var/run/mysql/mysql.sock
MYSQL_PORT 0
MYSQL_OPT 0
MYSQL_DATABASE postfix
MYSQL_USER_TABLE users
MYSQL_LOGIN_FIELD email
MYSQL_CLEAR_PWFIELD clear
MYSQL_UID_FIELD uid
MYSQL_GID_FIELD gid
MYSQL_HOME_FIELD homedir
MYSQL_MAILDIR_FIELD maildir
SASL library
创建/etc/postfix/sasl/smtpd.conf：
pwcheck_method: PAM
PAM-MySQL
创建/etc/pam.d/smtp：
auth optional pam_mysql.so host=localhost db=postfix user=mysql-postfix-user passwd=mysql-postfix-pass table=users usercolumn=email passwdcolumn=clear crypt=n
account required pam_mysql.so host=localhost db=postfix user=mysql-postfix-user passwd=mysql-postfix-pass usercolumn=email passwdcolumn=clear crypt=n
4、TLS支持
通过修改/usr/lib/ssl/misc/CA.pll脚本实现，以下修改后CA1.pl和未修改CA.pl之间的对比：
*** CA.pl
--- CA1.pl
***************
*** 59,69 ****
} elsif (/^-newcert$/)