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$/) {
# create a certificate
! system ("$REQ -new -x509 -keyout newreq.pem -out newreq.pem $DAYS");
$RET=$?;
print "Certificate (and private key) is in newreq.pem\n"
} elsif (/^-newreq$/) {
# create a certificate request
! system ("$REQ -new -keyout newreq.pem -out newreq.pem $DAYS");
$RET=$?;
print "Request (and private key) is in newreq.pem\n";
} elsif (/^-newca$/) {
--- 59,69 ----
} elsif (/^-newcert$/) {
# create a certificate
! system ("$REQ -new -x509 -nodes -keyout newreq.pem -out newreq.pem $DAYS");
$RET=$?;
print "Certificate (and private key) is in newreq.pem\n"
} elsif (/^-newreq$/) {
# create a certificate request
! system ("$REQ -new -nodes -keyout newreq.pem -out newreq.pem $DAYS");
$RET=$?;
print "Request (and private key) is in newreq.pem\n";
} elsif (/^-newca$/) {
现在就可以使用修改的CA1.pl来签发证书：
# cd /usr/local/ssl/misc
# ./CA1.pl -newca
# ./CA1.pl -newreq
# ./CA1.pl -sign
# cp demoCA/cacert.pem /etc/postfix/CAcert.pem
# cp newcert.pem /etc/postfix/cert.pem
# cp newreq.pem /etc/postfix/key.pem
修改main.cf，添加：
smtpd_tls_cert_file = /etc/postfix/cert.pem
smtpd_tls_key_file = /etc/postfix/privkey.pem
smtpd_use_tls = yes
tls_random_source = dev:/dev/urandom
tls_daemon_random_source = dev:/dev/urandom
重起postfix后就可以看到250-STARTTLS
很多邮件客户端对TLS的支持并不是非常好，建议使用stunnel来实现相应的smtp和pop3加密。
# apt-get install stunnel
证书：
# openssl req -new -x509 -days 365 -nodes -config /etc/ssl/openssl.cnf -out stunnel.pem -keyout stunnel.pem
# openssl gendh 512 >> stunnel.pem
服务端：
# stunnel -d 60025 -r 25 -s nobody -g nogroup
# stunnel -d 60110 -r 110 -s nobody -g nogroup
如果使用-n pop3等参数就只能用邮件客户端收信。
客户端：
建一个stunnel.conf文件：
client = yes
[pop3]
accept = 127.0.0.1:110
connect = 192.168.7.144:60110
[smtp]
accept = 127.0.0.1:25
connect = 192.168.7.144:60025
然后启动stunnel.exe，在邮件客户端的smtp和pop3的服务器都填127.0.0.1就可以了，这样从你到邮件服务器端的数据传输就让stunnel给你加密了。
5、测试用户
# mkdir -p /home/vmail/test.org/san/
# chown -R nobody.nogroup /home/vmail
# chmod -R 700 /home/vmail
mysql> use postfix
mysql> insert into transport set domain='test.org', destination='
virtual:';
mysql> insert into users set email='san@test.org',clear='test',name='',uid='65534',gid='65534',
homedir='home/vmail',maildir='test.org/san/';
然后就可以使用客户端收发邮件，记得用户名是email地址。