You appear to be saying there will be mail systems that need to send
mail to IPv4 systems, but will not have an IPv4 mail server so the
recipients can't reply to them. Really?
No, I'm saying that when IPv4 starts going away, there will be more and more
systems needing to send mail via NAT to such that client and server ends of
the connection have different address types.
Um, not to belabor the obvious, but I presume you know that to send
someone mail, their domain needs to publish an MX record that points to a
host with an A or AAAA record.
Could you explain in detail how I am supposed to send mail to people whose
mail servers are stuck behind a NAT64 without a fixed public address?
Alternatively, it sounds like you're confusing submission and SMTP relay
again. We all agree that you don't need to verify IPs or anything like
that for submission since submit clients identify themselves with AUTH.
John Levine, johnl(_at_)taugh(_dot_)com, Taughannock Networks, Trumansburg NY
Please consider the environment before reading this e-mail. https://jl.ly
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