Postfix - How to receive mails from one or a few Hosts only and disabling open relay or local domain

Question

I would Postfix to receive mail from my front antispam server host. Postfix does not act as open relay but if mails are sent to local domain, mails are delivered and this must be blocked. So goal is: Users can continue sending and receiving mail from postfix via authentication method. Disable local open relay Receive mails only from antispam host. thank you R

Answer 1

You may use Linux TCP/IP firewall to accept incoming SMTP connections only from allowes hosts/IP-addresses.