Prevent remote email from my own domain

[gramzon]

How can I block incoming email from remote servers with "mail from: *@mydomain.com" header where mydomain is a domain hosted on my server?
I tested this by executing

telnet mydomain.com 25

from a different server and set

mail from: [email protected]
rcpt to: [email protected]

The e-mail is accepted.
If I set the "rcpt to:" header to a remote domain, then the server properly responds with 550 not permitted to relay, because all users are required to authenticate to relay through my server, but I want all users to be forced to authenticate if the "mail from:" is a local address as well, regardless of recipient.

 

[cPanelLauren]

SPF and DKIM are in place to limit the ability of mail being sent this way. If the host isn't authorized to send for your domain it should fail SPF, same issue if the DKIM signature isn't found. You can also choose to deny DKIM failures in Exim.

What it sounds like you're referencing is a relay: Stop Mail Relay - this thread goes over open relays.