[WriteLog] Email Blocked

[Jim Preston]

I sent a message to the Writelog list, as a reply to another message. It 
was blocked somewhere along the line. Does anyone know what might have 
caused it?  Here is the error message:

73,

Jim N6VH
--------------------------------------------------------------------------------


This is the mail system at host mx.tcnc.com.

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

<writelog at contesting.com>: host mx.contesting.com[2001:470:1:313::220] said:
     550 5.7.1 Service unavailable; client [2600:3c03::f03c:91ff:fe0c:9b6]
     blocked using zen.spamhaus.org (in reply to RCPT TO command)


Reporting-MTA: dns; mx.tcnc.com
X-Postfix-Queue-ID: 31A2B205F
X-Postfix-Sender: rfc822; jpreston1 at cox.net
Arrival-Date: Fri, 19 Apr 2019 14:21:52 +0000 (UTC)

Final-Recipient: rfc822; writelog at contesting.com
Original-Recipient: rfc822;writelog at contesting.com
Action: failed
Status: 5.7.1
Remote-MTA: dns; mx.contesting.com
Diagnostic-Code: smtp; 550 5.7.1 Service unavailable; client
     [2600:3c03::f03c:91ff:fe0c:9b6] blocked using zen.spamhaus.org