I tried to respond directly to Fred, but got bounced. Hence replying to the list even though, as Fred notes, this is WAY off topic.
Bill:
I'm using milter-greylist, so that any site sending mail that is not in its whitelist database will get a 451 response code, which means "cannot accept mail now, try again later" (my own wording). Any modern SMTP agent should be smart enough to try again after a while. Once that retry has been received, that site will be auto-whitelisted for 24 hours, so that sites that send multiple emails a day remain whitelisted and don't have to go thru that hassle.
Fred
If that is not what you got, then I don't know why it would bounce.
Hi Fred - I tried again, and it bounced again. This is not a 451 as you mentioned above, so I did not retry. Here is what I got back:
==================== Reporting-MTA: dns; smtp-auth.no-ip.com X-Postfix-Queue-ID: AA3B137FAE0 X-Postfix-Sender: rfc822; bgee@campercaver.net Arrival-Date: Wed, 26 Feb 2020 04:40:27 -0800 (PST)
Final-Recipient: rfc822; fredex@fcshome.stoneham.ma.us Original-Recipient: rfc822;fredex@fcshome.stoneham.ma.us Action: failed Status: 5.3.0 Remote-MTA: dns; mx0.uce-less.net Diagnostic-Code: smtp; 553 5.3.0 fredex@fcshome.stoneham.ma.us... Spam blocked - see http://www.uce-less.net/dnsbl ====================
I tried to open the URL given in the reject message, but that also fails. The message is "The requested URL /dnsbl was not found on this server."
Bill Gee