How can I secure port 25 in postfix/dovecot? Right now, I can send internal email through telnet without login. For example:
telnet mydomain.com 25
MAIL FROM:<me@mydomain.com>
250 2.1.0 Ok
RCPT TO:<you@mydomain.com>
250 2.1.5 Ok
Right now, everyone can send emails without login. All I want is that, emails can only be sent when user logged in.
How can I make it something like "Relay access denied" if I am not logged in.