To blacklist an alias:

```bash
echo "alias@ketrenos.com reject" | sudo tee -a /etc/postfix/recipient_restrictions
sudo postmap hash:/etc/postfix/recipient_restrictions
sudo systemctl restart postfix
```

To black list a sender:

```bash
echo "name@address.com" | sudo tee -a /etc/postfix/sender_restrictions
sudo postmap hash:/etc/postfix/sender_restrictions
sudo systemctl restart postfix
```

To add a sender (eg firsttechfed.com) to the whitelist of sender DNS:

```bash
echo "firsttechfed.com OK" | sudo tee -a /etc/postfix/sender_checks
sudo postmap hash:/etc/postfix/sender_checks
sudo systemctl restart postfix
```

To add a new alias, append entries to /etc/aliases and run:

```bash
echo "alias: user" | sudo tee -a /etc/postfix/aliases
sudo postalias /etc/postfix/aliases
sudo systemctl restart postfix
```