I have a postfix 3.5.2 system that accepts messages from internal hosts and relays to internal destinations and to an email perimeter that delivers to external (Internet) domains.
The issue I'm seeing is regarding external domains that do not follow DNS best practices and have CNAME records published for the same domain that their MX records are published for. What I end up with is the recipient being changed from the intended domain to the value of the published CNAME. The intended external domain is: bizpro.cn I have no intentional address rewriting on this system, and based on that, I do not expect this behavior. Is there a known solution besides adding a manual rewrite for this recipient domain? Sanitized mail log below. Sep 2 01:35:39 mailhost postfix/smtpd[25660]: 4cGDwq3YqbzjB8nV: client=unknown[x.x.x.x] Sep 2 01:35:39 mailhost postfix/cleanup[26989]: 4cGDwq3YqbzjB8nV: warning: header Received: from use1otomprd01 (unknown [x.x.x.x])??by mailhost (Postfix) with ESMTPS id 4cGDwq3YqbzjB8nV??for <katherine...@web.b51.vhostgo.com>; Tue, 2 Sep 2025 0 from unknown[x.x.x.x]; from=<mg-procurement-operat...@example.com> to=<katherine...@web.b51.vhostgo.com> proto=ESMTP helo=<use1otomprd01> Sep 2 01:35:39 mailhost postfix/cleanup[26989]: 4cGDwq3YqbzjB8nV: warning: header Received: (from otosadm@localhost)??by use1otomprd01 (8.15.2/8.14.7/Submit) id 5825ZbvF012075??for katherine...@bizpro.cn; Tue, 2 Sep 2025 01:35:37 -0400 from unknown[x.x.x.x]; from=<mg-procurement-operat...@example.com> to=<katherine...@web.b51.vhostgo.com> proto=ESMTP helo=<use1otomprd01> Sep 2 01:35:39 mailhost postfix/cleanup[26989]: 4cGDwq3YqbzjB8nV: message-id=<202509020535.5825ZbvF012075@use1otomprd01> Sep 2 01:35:39 mailhost postfix/cleanup[26989]: 4cGDwq3YqbzjB8nV: warning: header From: no-re...@example.com from unknown[x.x.x.x]; from=<mg-procurement-operat...@example.com> to=<katherine...@web.b51.vhostgo.com> proto=ESMTP helo=<use1otomprd01> Sep 2 01:35:39 mailhost postfix/qmgr[8958]: 4cGDwq3YqbzjB8nV: from=<mg-procurement-operat...@example.com>, size=952387, nrcpt=1 (queue active) Sep 2 01:35:39 mailhost postfix/smtp[27076]: 4cGDwq3YqbzjB8nV: to=<katherine...@web.b51.vhostgo.com>, relay=externaldelivery.example.com[y.y.y.y]:25, delay=0.35, delays=0.09/0/0.08/0.18, dsn=2.0.0, status=sent (250 ok: Message 3591085 accepted) Chris John ________________________________ This message (including any attachments) may contain confidential, proprietary, privileged and/or private information. The information is intended to be for the use of the individual or entity designated above. If you are not the intended recipient of this message, please notify the sender immediately, and delete the message and any attachments. Any disclosure, reproduction, distribution or other use of this message or any attachments by an individual or entity other than the intended recipient is prohibited.
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