On 08.09.25 18:37, John, Chris via Postfix-users wrote:
> 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.
On Wed, Sep 10, 2025 at 11:52:03AM +0200, Matus UHLAR - fantomas via
Postfix-users wrote:
This is not about following best practices. This is clearly violation of DNS
On 14.09.25 11:03, Viktor Dukhovni via Postfix-users wrote:
No, not a violation of DNS, rather such a rewrite is a violation of
RFC2321 (and its successors: 5321, 5321bis[1]) which changed the
semantics of CNAME-valued address domain parts from RFC821.
it IS a violation of DNS at least since RFC973, which says:
If a node has a CNAME RR, it should have no other RRs.
further RFCs (1034, 2181) support this as well.
Domain bizpro.cn violates this RFC:
bizpro.cn. 3600 IN MX 10 mx1-n.global-mail.cn.
bizpro.cn. 3600 IN MX 5 mx-n.global-mail.cn.
bizpro.cn. 3600 IN TXT "v=spf1 include:spf.global-mail.cn
~all"
bizpro.cn. 86400 IN NS dns19.hichina.com.
bizpro.cn. 86400 IN NS dns20.hichina.com.
bizpro.cn. 600 IN CNAME jsdzwy233com.gotoip2.com.
So, while the OPs problem is caused by sendmail processing, there's DNS
violation as well.
--
Matus UHLAR - fantomas, uh...@fantomas.sk ; http://www.fantomas.sk/
Warning: I wish NOT to receive e-mail advertising to this address.
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in first quarter of year 1901
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