Re: [Emailcore] Ticket #50: Use of top level domains in SMTP

John Levine <johnl@taugh.com> Fri, 23 July 2021 22:41 UTC

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Date: Fri, 23 Jul 2021 18:40:59 -0400
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From: John Levine <johnl@taugh.com>
To: emailcore@ietf.org
Cc: john-ietf@jck.com
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Subject: Re: [Emailcore] Ticket #50: Use of top level domains in SMTP
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It appears that John C Klensin  <john-ietf@jck.com> said:
>On a possibly-related topic, the DNSOP WG is considering
>proposals to officially allow private-use strings as top level
>domains.  If those proposals are approved, is it necessary to
>add language to either the discussion of FQDNs in RFC5321bis
>(noting that ticket #41 has been closed) or to add language to
>the A/S to be clear that MTAs are expected to not let such
>things escape onto the public Internet, just as they are
>expected to prevent such addresses as example@local and
>user@example.local from escaping.

I don't see why mail is special here.  Why is it any different
from a domain in a web page?

For that matter, if I send a message with mailto: adddresses in an
HTML body, or an attached PDF that includes javascript that shows
clickable e-mail addresses, some of which are local, how hard should
the MTA try to keep them from escaping? Let's not.

R's,
John