How to blacklist mails using Centos Web Panel / Centos ?

I would like to know how can we blacklist mails so that they do not come into our mail box in Centos 7 or using Centos Web Panel.

Thanks in advance.

in /etc/postfix/main.cf

smtpd_relay_restrictions = check_sender_access hash:/etc/postfix/sender_blacklist

In /etc/postfix/sender_blacklist

   email1@yahoo.com            REJECT
   email2@gmail.com            REJECT
   email3@outlook.com            REJECT
   email4@domain.tld            REJECT

postmap hash:/etc/postfix/sender_blacklist
service postfix reload

Jae,

Thanks for responding.

There is no /etc/postfix/sender_blacklist file, Do I need to create it ?

Is there no way to add blacklist in Centos web panel or via webmail ?