Undelivered Mail Returned to Sender

From: Mail Delivery System <MAILER-DAEMON_at_FreeBSD.org>
Date: Sat, 25 Sep 2021 19:56:01 +0000 (UTC)
This is the mail system at host mx1.freebsd.org.

I'm sorry to have to inform you that your message could not
be delivered to one or more recipients. It's attached below.

For further assistance, please send mail to postmaster.

If you do so, please include this problem report. You can
delete your own text from the attached returned message.

                   The mail system

<freebsd-isp_at_mlmmj.nyi.freebsd.org> (expanded from <freebsd-isp_at_freebsd.org>):
    host mlmmj.nyi.freebsd.org[2610:1c1:1:606c::50:24] said: 554 5.7.1 Spam
    message rejected (in reply to end of DATA command)

attached mail follows:

The original message was received at Sat, 25 Sep 2021 22:55:58 +0200
from freebsd.org []

----- The following addresses had permanent fatal errors -----

----- Transcript of session follows -----
  while talking to freebsd.org.:
>>> MAIL From:freebsd-isp_at_freebsd.org
<<< 501 freebsd-isp_at_freebsd.org... Refused

Received on Sat Sep 25 2021 - 19:56:01 UTC

Original text of this message