root@PLAY ~]# mkdir -p /root/.certs/                           ####创建目录，用来存放证书
[root@PLAY ~]# echo -n | openssl s_client -connect smtp.163.com:465 | sed -ne '/-BEGIN CERTIFICATE-/,/-END CERTIFICATE-/p' > ~/.certs/163.crt ####向163请求证书
depth=2 C = US, O = GeoTrust Inc., CN = GeoTrust Global CA
verify return:1
depth=1 C = US, O = GeoTrust Inc., CN = GeoTrust SSL CA - G3
verify return:1
depth=0 C = CN, ST = Zhejiang, L = Hangzhou, O = "NetEase (Hangzhou) Network Co., Ltd", OU = MAIL Dept., CN = *.163.com
verify return:1
DONE
[root@PLAY ~]# certutil -A -n "GeoTrust SSL CA" -t "C,," -d ~/.certs -i ~/.certs/163.crt                  ####添加一个证书到证书数据库中
[root@PLAY ~]# certutil -A -n "GeoTrust Global CA" -t "C,," -d ~/.certs -i ~/.certs/163.crt               ####添加一个证书到证书数据库中
[root@PLAY ~]# certutil -L -d /root/.certs                                                                                         ####列出目录下证书
Certificate Nickname Trust Attributes
SSL,S/MIME,JAR/XPI
GeoTrust SSL CA