CentOS 8.x postfix block incoming emails from domain or address

To block incoming emails from sender or domain in postfix use:

Use following in main.cf

smtpd_relay_restrictions = permit_mynetworks,
permit_sasl_authenticated,
check_sender_access hash:/etc/postfix/access,
reject_unauth_destination

Use following in /etc/postfix/access
```
user@domain.com     REJECT
```
Recreate access index:
```
postmap access
```
One time reload of postfix for accounting for main.cf changes:
```
systemctl reload postfix
```

Refer:

Anonymous