I have been having issues sending mail to [users]@stx.rr.com from my domain hosted by a2hosting. After about 5-hours, I receive an undeliverable mail message including:
Final-Recipient: rfc822; [user]@stx.rr.com Original-Recipient: rfc822;[user]@stx.rr.com Action: failed Status: 4.2.0 Remote-MTA: dns; pkvw-mx.msg.pkvw.co.charter.net Diagnostic-Code: smtp; 451 4.2.0 <email@example.com> sender rejected AUP#CMSNDR
I have checked my domain through mxtoolbox.com diagnostics and there are no known blacklist issues. I can send mail though accounts with hotmail and Earthlink without issue. Might this have been noticed by anyone else?
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I appreciate the response, however the problem I experienced had to do with inbound mail to rr.com recipients. I took the issue up with my smtp provider a2hosting and they, as well as tools at mxtoolbox, found no issues regarding the routing of messages originating from my domain. What I have never gotten an answer from anyone regards the routing indicated in the bouce response:
Reporting-MTA: dns; relay.mailchannels.net X-Postfix-Queue-ID: CE19A5021A8 X-Postfix-Sender: rfc822; firstname.lastname@example.org Arrival-Date: Tue, 19 Nov 2019 14:02:31 +0000 (UTC) Final-Recipient: rfc822; [user]@stx.rr.com Original-Recipient: rfc822;[user]@stx.rr.com Action: failed Status: 4.2.0 Remote-MTA: dns; pkvw-mx.msg.pkvw.co.charter.net Diagnostic-Code: smtp; 451 4.2.0 <email@example.com> sender rejected AUP#CMSNDR
How, or why it transits through relay.mailchannels.net is actually my question. Since this is no longer occuring, I must assume it was a transitory issue and can only hope that does not reoccur.
I finally found that my SMTP provider is routing mail through "relay.mailchannels.net" that were being tagged with an SPF soft-fail. How those flagged messages are treated by the recipent's host varies. Some receiving hosts, apparently including Charter, simply discard them rather than bounce them.
I resolved this by adding an SPF entry to my DNS zone file allowing transit through "relay.mailchannels.net" on my host system and now get clean headers and my problem solved.