I have a postfix mail server that has been working great for some time. I started to notice some weird logs for postfix in the /var/log/mail.log. Seems like the log is a message saying that my server was detected as spam so it was blocked.

postfix/smtp[12217]: 748253FC69: [email protected], relay=alt1.gmail-smtp-in.l.google.com[]:25, delay=330322, delays=330302/12/6/2.3, dsn=4.7.0, status=deferred (host alt1.gmail-smtp-in.l.google.com[]

My mailservers are not configured to send outbound mail. There should be no outgoing mail only incoming. So not sure how these logs are showing up. Seems like my server is sending random emails out?

Anyway to see what is actually sending these emails like an email address?

Seems there are many of these emails.

Any help would be appreciated.

Thank you.

1 Answer 1


It's possible your server is configured as an open relay. So an outsider can connect to your server and say "send this message to gmail". Your machine accepts it and relays it on.

If you check in your logs before that line you might see lines similar to this:

Jul 24 17:51:15 SERVER postfix/smtpd[17418]: connect from unknown[]
Jul 24 17:51:21 SERVER postfix/smtpd[17418]: NOQUEUE: reject: RCPT from unknown[]: 454 4.7.1 <[email protected]>: Relay access denied; from=<info@MYDOMAIN> to=<[email protected]> proto=ESMTP helo=<WIN-6H79TFFJL6O>
Jul 24 17:51:21 SERVER postfix/smtpd[17418]: lost connection after RCPT from unknown[]
Jul 24 17:51:21 SERVER postfix/smtpd[17418]: disconnect from unknown[]

In this case my server correctly detected an outsider was trying to relay through me (pretending to be from my email domain) and rejected it. If I hadn't set up my relay rules set up properly then this message would have been sent.

  • I do not see any relay access in the logs. How would you configure it to close this relay?
    – bob Ditusa
    Commented Jul 26, 2020 at 13:52
  • I can see like the emails that are being sent out. I am assu,ing some sort of relay is being set up
    – bob Ditusa
    Commented Jul 26, 2020 at 13:59
  • How would you block this relay. Sorry I am new to postfix.
    – bob Ditusa
    Commented Jul 26, 2020 at 14:46
  • 1
    Start here: postfix.org/BASIC_CONFIGURATION_README.html Commented Jul 26, 2020 at 15:05

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