How to use postfix to send emails in centos7

[root@mail ~]# yum -y install postfix mailx
[root@mail ~]# systemctl start postfix
[root@mail ~]# systemctl enable postfix
[root@mail ~]# netstat -anput | grep 25
tcp        0      0 0.0.0.0:25              0.0.0.0:*               LISTEN      1820/master

[root@mail ~]# vim /etc/postfix/main.cf
myhostname = mail.mds.com
mydomain = mds.com
myorigin = $mydomain
inet_interfaces = all
mydestination = $myhostname,$mydomain

[root@mail ~]# mkdir /root/.certs
[root@mail ~]# echo -n | openssl s_client -connect smtp.163.com:465 | sed -ne '/-BEGIN CERTIFICATE-/,/-END CERTIFICATE-/p' > ~/.certs/163.crt
[root@mail ~]# certutil -A -n "GeoTrust Global CA" -t "C,," -d ~/.certs -i ~/.certs/163.crt
[root@mail ~]# certutil -A -n "GeoTrust SSL CA" -t "C,," -d ~/.certs -i ~/.certs/163.crt
[root@mail ~]# certutil -L -d /root/.certs
[root@mail ~]# certutil -A -n "GeoTrust SSL CA - G3" -t "Pu,Pu,Pu" -d ~/.certs/ -i ~/.certs/163.crt

[root@mail ~]# vim /etc/mail.rc
set ssl-verify="ignore"
set smtp-auth="login"
set from="mds302587@163.com"
set smtp="smtps://smtp.163.com:465"
set smtp-auth-user="mds302587@163.com"
set smtp-auth-password="123456"
set nss-config-dir="/root/.certs"

[root@mail ~]# systemctl restart postfix
[root@mail ~]# echo "This is a test mail" | mail -s '邮件测试' 452666750@qq.com