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:<[email protected]>
250 2.1.0 Ok
RCPT TO:<[email protected]>
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.


1 Answer 1


This is the postfix mynetworks option. You probably want to set it to, that way only programs running on your server can send mail without logging in first.

  • I still can do a telnet outside of my network. And it succeed.
    – Maximilian
    Dec 8, 2015 at 22:02

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