Solution: https: //blog.csdn.net/pheng5/article/details/79975455
Solution: vi /etc/postfix/main.cf
Found configured to:
inet_interfaces = localhost
inet_protocols = all
Read:
inet_interfaces = all
Or inet_interfaces = 127.0.0.1
inet_protocols = all
Restart the postfix service can be
systemctl start postfix
Remember to restart after the execution.