On Thursday 2 January 2020 19:51:09 CET, Keith Moore wrote:
It's when the mail is relayed between mail domains that the
standards need to provide guidance, because when sending domain
and receiving domain have different assumptions about what is
right, it causes unnecessary failures.
I feel that a brief digression might help to prolong this discussion.
One way to disagree is about IP address family.
If I remember correctly, nothing (else) in 5321/2 requires a v6-only host
to understand anything about v4. Running a v6-only host is stupid at this
point, perhaps slightly less stupid in five years, but even so I don't
think the next RFCs should feature an IPv4 requirement for address
literals, and nothing for the main parts of the protocols.
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