On Fri, Oct 18, 2024 at 10:14:00AM +0200, Ted Lemon wrote:
> That's fair, but it seems like then it might be good to actually say
> that in the document. As an implementor I would be inclined to treat a
> CNAME here as invalid and ignore it based on the text as written.
Can you suggest text that manages to both discourage publication of
CNAME-valued MX "exchange" names, and slightly nudges implementors to
tolerate these, based on today ~1% of domains being in violation of this
advice.
[ I consider 1% too large a fraction to ignore, but if others feel that
this is low enough to proceed to punish them for their negligence,
perhaps MUST is how that 1% could over time (O(decade or two)) be
brought closer to zero. ]
Examples:
0. idaho.gov. IN MX 10 inbound.idaho.gov.
;
inbound.idaho.gov. IN CNAME us-smtp-inbound-1.mimecast.com.
us-smtp-inbound-1.mimecast.com. IN A 170.10.128.141
us-smtp-inbound-1.mimecast.com. IN A 170.10.128.221
us-smtp-inbound-1.mimecast.com. IN A 170.10.128.242
us-smtp-inbound-1.mimecast.com. IN A 205.139.110.141
us-smtp-inbound-1.mimecast.com. IN A 205.139.110.221
us-smtp-inbound-1.mimecast.com. IN A 205.139.110.242
1. gmt.io. IN MX 10 mail.gmt.io.
;
mail.gmt.io. IN CNAME mail.hetzner.gmt.io.
mail.hetzner.gmt.io. IN A 135.181.193.235
2. mijnenergie.be. IN MX 1 mijnenergie-be.mail.protection.outlook.com.
mijnenergie.be. IN MX 5 mail.mijnenergie.be.
mijnenergie.be. IN MX 10 backupmail.mijnenergie.be.
;
mail.mijnenergie.be. IN CNAME pop3.mailprotect.be.
pop3.mailprotect.be. IN CNAME pop.mailprotect.be.
pop.mailprotect.be. IN CNAME smtp.mailprotect.be.
smtp.mailprotect.be. IN A 178.208.39.146
smtp.mailprotect.be. IN A 178.208.39.149
smtp.mailprotect.be. IN A 178.208.39.154
smtp.mailprotect.be. IN A 178.208.39.157
smtp.mailprotect.be. IN A 178.208.39.158
--
Viktor.
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