On 2023-12-01 John R Levine via Exim-users <exim-users@???> wrote:
> It appears that Jeremy Harris via Exim-users <jgh@???> said:
[...]
> > Our log says that message was aimed at exim-users@???
> Oh, I see the problem. lists.exim.org is a CNAME for cumin.exim.org,
> and qmail is standard compliant per RFC 1123:
> 5.2.2 Canonicalization: RFC-821 Section 3.1
> The domain names that a Sender-SMTP sends in MAIL and RCPT
> commands MUST have been "canonicalized," i.e., they must be
> fully-qualified principal names or domain literals, not
> nicknames or domain abbreviations. A canonicalized name either
> identifies a host directly or is an MX name; it cannot be a
> CNAME.
> When I put in an explicit route it uses that rather than resolving the CNAME,
> unrelated to IPv6.
> It's poor form to use a CNAME as a mail domain, and worse form not to
> do what the standard says, but I suppose that horse left the barn a
> long time ago.
Hello,
Afaict this part of rfc1123 has been superseded by RFC 2821 [1] anno 2001
which explicitely allows CNAMES.
cu Andreas
[1] since superseded by rfc 5321
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